diff --git a/beacon_chain/beacon_chain_db.nim b/beacon_chain/beacon_chain_db.nim
index 946bae97f..4c929f4ae 100644
--- a/beacon_chain/beacon_chain_db.nim
+++ b/beacon_chain/beacon_chain_db.nim
@@ -108,4 +108,4 @@ iterator getAncestors*(db: BeaconChainDB, root: Eth2Digest):
   while (let blck = db.getBlock(root); blck.isSome()):
     yield (root, blck.get())
 
-    root = blck.get().parent_root
+    root = blck.get().previous_block_root
diff --git a/beacon_chain/beacon_node.nim b/beacon_chain/beacon_node.nim
index 5ca9e7ada..3bed51190 100644
--- a/beacon_chain/beacon_node.nim
+++ b/beacon_chain/beacon_node.nim
@@ -290,13 +290,13 @@ proc proposeBlock(node: BeaconNode,
   # To create a block, we'll first apply a partial block to the state, skipping
   # some validations.
   var blockBody = BeaconBlockBody(
+    randao_reveal: validator.genRandaoReveal(node.state.data, slot),
+    eth1_data: node.mainchainMonitor.getBeaconBlockRef(),
     attestations: node.attestationPool.getAttestationsForBlock(slot))
 
   var newBlock = BeaconBlock(
     slot: slot,
-    parent_root: node.state.blck.root,
-    randao_reveal: validator.genRandaoReveal(node.state.data, slot),
-    eth1_data: node.mainchainMonitor.getBeaconBlockRef(),
+    previous_block_root: node.state.blck.root,
     body: blockBody,
     signature: ValidatorSig(), # we need the rest of the block first!
     )
@@ -325,7 +325,7 @@ proc proposeBlock(node: BeaconNode,
   info "Block proposed",
     slot = humaneSlotNum(slot),
     stateRoot = shortLog(newBlock.state_root),
-    parentRoot = shortLog(newBlock.parent_root),
+    parentRoot = shortLog(newBlock.previous_block_root),
     validator = shortValidatorKey(node, validator.idx),
     idx = validator.idx
 
@@ -537,7 +537,7 @@ proc onBeaconBlock(node: BeaconNode, blck: BeaconBlock) =
     blockRoot = shortLog(blockRoot),
     slot = humaneSlotNum(blck.slot),
     stateRoot = shortLog(blck.state_root),
-    parentRoot = shortLog(blck.parent_root),
+    parentRoot = shortLog(blck.previous_block_root),
     signature = shortLog(blck.signature),
     proposer_slashings = blck.body.proposer_slashings.len,
     attester_slashings = blck.body.attester_slashings.len,
@@ -549,7 +549,7 @@ proc onBeaconBlock(node: BeaconNode, blck: BeaconBlock) =
   if not node.blockPool.add(node.state, blockRoot, blck):
     # TODO the fact that add returns a bool that causes the parent block to be
     #      pre-emptively fetched is quite ugly - fix.
-    node.fetchBlocks(@[blck.parent_root])
+    node.fetchBlocks(@[blck.previous_block_root])
 
   # The block we received contains attestations, and we might not yet know about
   # all of them. Let's add them to the attestation pool - in case they block
diff --git a/beacon_chain/block_pool.nim b/beacon_chain/block_pool.nim
index 7d14c335f..bd4a0da2c 100644
--- a/beacon_chain/block_pool.nim
+++ b/beacon_chain/block_pool.nim
@@ -100,7 +100,7 @@ proc init*(T: type BlockPool, db: BeaconChainDB): BlockPool =
     finalizedHead =
       headRef.findAncestorBySlot(headState.finalized_epoch.get_epoch_start_slot())
     justifiedHead =
-      headRef.findAncestorBySlot(headState.justified_epoch.get_epoch_start_slot())
+      headRef.findAncestorBySlot(headState.current_justified_epoch.get_epoch_start_slot())
 
   doAssert justifiedHead.slot >= finalizedHead.slot,
     "justified head comes before finalized head - database corrupt?"
@@ -162,7 +162,7 @@ proc add*(
 
     return true
 
-  let parent = pool.blocks.getOrDefault(blck.parent_root)
+  let parent = pool.blocks.getOrDefault(blck.previous_block_root)
 
   if parent != nil:
     # The block might have been in either of these - we don't want any more
@@ -197,7 +197,7 @@ proc add*(
     let
       justifiedBlock =
         blockRef.findAncestorBySlot(
-          state.data.justified_epoch.get_epoch_start_slot())
+          state.data.current_justified_epoch.get_epoch_start_slot())
 
     if not justifiedBlock.justified:
       info "Justified block",
@@ -227,7 +227,7 @@ proc add*(
   #      think are useful - but, it would also risk filling the database with
   #      junk that's not part of the block graph
 
-  if blck.parent_root in pool.unresolved:
+  if blck.previous_block_root in pool.unresolved:
     return true
 
   # This is an unresolved block - put it on the unresolved list for now...
@@ -244,7 +244,7 @@ proc add*(
     blck = shortLog(blck),
     blockRoot = shortLog(blockRoot)
 
-  pool.unresolved[blck.parent_root] = UnresolvedBlock()
+  pool.unresolved[blck.previous_block_root] = UnresolvedBlock()
   pool.pending[blockRoot] = blck
 
   false
@@ -303,8 +303,8 @@ proc checkUnresolved*(pool: var BlockPool): seq[Eth2Digest] =
 proc skipAndUpdateState(
     state: var BeaconState, blck: BeaconBlock, flags: UpdateFlags,
     afterUpdate: proc (state: BeaconState)): bool =
-  skipSlots(state, blck.parent_root, blck.slot - 1, afterUpdate)
-  let ok  = updateState(state, blck.parent_root, blck, flags)
+  skipSlots(state, blck.previous_block_root, blck.slot - 1, afterUpdate)
+  let ok  = updateState(state, blck.previous_block_root, blck, flags)
 
   afterUpdate(state)
 
@@ -337,7 +337,7 @@ proc updateState*(
 
   # Common case: the last thing that was applied to the state was the parent
   # of blck
-  if state.blck.root == ancestors[0].data.parent_root and
+  if state.blck.root == ancestors[0].data.previous_block_root and
       state.data.slot < blck.slot:
     let ok = skipAndUpdateState(
         state.data, ancestors[0].data, {skipValidation}) do (state: BeaconState):
@@ -395,12 +395,12 @@ proc updateState*(
     let last = ancestors[i]
 
     skipSlots(
-        state.data, last.data.parent_root,
+        state.data, last.data.previous_block_root,
         last.data.slot - 1) do(state: BeaconState):
       pool.maybePutState(state)
 
     let ok = updateState(
-        state.data, last.data.parent_root, last.data, {skipValidation})
+        state.data, last.data.previous_block_root, last.data, {skipValidation})
     doAssert ok,
       "We only keep validated blocks in the database, should never fail"
 
@@ -443,7 +443,7 @@ proc updateHead*(pool: BlockPool, state: var StateData, blck: BlockRef) =
     stateRoot = shortLog(state.root),
     headBlockRoot = shortLog(state.blck.root),
     stateSlot = humaneSlotNum(state.data.slot),
-    justifiedEpoch = humaneEpochNum(state.data.justified_epoch),
+    justifiedEpoch = humaneEpochNum(state.data.current_justified_epoch),
     finalizedEpoch = humaneEpochNum(state.data.finalized_epoch)
 
   let
diff --git a/beacon_chain/spec/beaconstate.nim b/beacon_chain/spec/beaconstate.nim
index b1bb0f26e..25241e4dc 100644
--- a/beacon_chain/spec/beaconstate.nim
+++ b/beacon_chain/spec/beaconstate.nim
@@ -10,8 +10,8 @@ import
   ../extras, ../ssz,
   ./crypto, ./datatypes, ./digest, ./helpers, ./validator
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_effective_balance
-func get_effective_balance*(state: BeaconState, index: ValidatorIndex): uint64 =
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_effective_balance
+func get_effective_balance*(state: BeaconState, index: ValidatorIndex): Gwei =
   ## Return the effective balance (also known as "balance at stake") for a
   ## validator with the given ``index``.
   min(state.validator_balances[index], MAX_DEPOSIT_AMOUNT)
@@ -61,13 +61,13 @@ func process_deposit(state: var BeaconState, deposit: Deposit) =
 
     state.validator_balances[index] += amount
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_delayed_activation_exit_epoch
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_delayed_activation_exit_epoch
 func get_delayed_activation_exit_epoch*(epoch: Epoch): Epoch =
   ## Return the epoch at which an activation or exit triggered in ``epoch``
   ## takes effect.
   epoch + 1 + ACTIVATION_EXIT_DELAY
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#activate_validator
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#activate_validator
 func activate_validator(state: var BeaconState,
                         index: ValidatorIndex,
                         is_genesis: bool) =
@@ -81,7 +81,7 @@ func activate_validator(state: var BeaconState,
     else:
       get_delayed_activation_exit_epoch(get_current_epoch(state))
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#initiate_validator_exit
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#initiate_validator_exit
 func initiate_validator_exit*(state: var BeaconState,
                               index: ValidatorIndex) =
   ## Initiate exit for the validator with the given ``index``.
@@ -107,7 +107,7 @@ func reduce_balance*(balance: var uint64, amount: uint64) =
   # Not in spec, but useful to avoid underflow.
   balance -= min(amount, balance)
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#slash_validator
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#slash_validator
 func slash_validator*(state: var BeaconState, index: ValidatorIndex) =
   ## Slash the validator with index ``index``.
   ## Note that this function mutates ``state``.
@@ -155,7 +155,22 @@ func update_shuffling_cache*(state: var BeaconState) =
     state.shuffling_cache.shuffling_1 = shuffling_seq
   state.shuffling_cache.index = 1 - state.shuffling_cache.index
 
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_temporary_block_header
+func get_temporary_block_header*(blck: BeaconBlock): BeaconBlockHeader =
+  ## Return the block header corresponding to a block with ``state_root`` set
+  ## to ``ZERO_HASH``.
+  BeaconBlockHeader(
+    slot: blck.slot.uint64,
+    previous_block_root: blck.previous_block_root,
+    state_root: ZERO_HASH,
+    block_body_root: hash_tree_root_final(blck.body),
+    signature: blck.signature)
+
 # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#on-genesis
+func get_empty_block*(): BeaconBlock =
+  # Nim default values fill this in fine, mostly.
+  result.slot = GENESIS_SLOT
+
 func get_genesis_beacon_state*(
     genesis_validator_deposits: openArray[Deposit],
     genesis_time: uint64,
@@ -204,7 +219,7 @@ func get_genesis_beacon_state*(
 
     # Finality
     previous_justified_epoch: GENESIS_EPOCH,
-    justified_epoch: GENESIS_EPOCH,
+    current_justified_epoch: GENESIS_EPOCH,
     justification_bitfield: 0,
     finalized_epoch: GENESIS_EPOCH,
 
@@ -214,6 +229,7 @@ func get_genesis_beacon_state*(
     # Recent state
     # latest_block_roots, latest_active_index_roots, latest_slashed_balances,
     # latest_attestations, and batched_block_roots automatically initialized.
+    latest_block_header: get_temporary_block_header(get_empty_block()),
   )
 
   for i in 0 ..< SHARD_COUNT:
@@ -251,14 +267,14 @@ func get_initial_beacon_block*(state: BeaconState): BeaconBlock =
     # initialized to default values.
   )
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_block_root
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_block_root
 func get_block_root*(state: BeaconState,
                      slot: Slot): Eth2Digest =
   # Return the block root at a recent ``slot``.
 
-  doAssert state.slot <= slot + LATEST_BLOCK_ROOTS_LENGTH
+  doAssert state.slot <= slot + SLOTS_PER_HISTORICAL_ROOT
   doAssert slot < state.slot
-  state.latest_block_roots[slot mod LATEST_BLOCK_ROOTS_LENGTH]
+  state.latest_block_roots[slot mod SLOTS_PER_HISTORICAL_ROOT]
 
 # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_attestation_participants
 func get_attestation_participants*(state: BeaconState,
@@ -304,17 +320,26 @@ func process_ejections*(state: var BeaconState) =
   ## Iterate through the validator registry and eject active validators with
   ## balance below ``EJECTION_BALANCE``
   for index in get_active_validator_indices(
-      # Spec bug in 0.4.0: is just current_epoch(state)
       state.validator_registry, get_current_epoch(state)):
     if state.validator_balances[index] < EJECTION_BALANCE:
       exit_validator(state, index)
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_total_balance
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_total_balance
 func get_total_balance*(state: BeaconState, validators: auto): Gwei =
   # Return the combined effective balance of an array of validators.
   foldl(validators, a + get_effective_balance(state, b), 0'u64)
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#validator-registry-and-shuffling-seed-data
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#validator-registry-and-shuffling-seed-data
+func should_update_validator_registry*(state: BeaconState): bool =
+  # Must have finalized a new block
+  if state.finalized_epoch <= state.validator_registry_update_epoch:
+    return false
+  # Must have processed new crosslinks on all shards of the current epoch
+  allIt(0 ..< get_current_epoch_committee_count(state).int,
+        not (state.latest_crosslinks[
+          ((state.current_shuffling_start_shard + it.uint64) mod
+            SHARD_COUNT).int].epoch <= state.validator_registry_update_epoch))
+
 func update_validator_registry*(state: var BeaconState) =
   ## Update validator registry.
   ## Note that this function mutates ``state``.
@@ -389,7 +414,7 @@ proc checkAttestation*(
 
   let expected_justified_epoch =
     if slot_to_epoch(attestation.data.slot + 1) >= get_current_epoch(state):
-      state.justified_epoch
+      state.current_justified_epoch
     else:
       state.previous_justified_epoch
 
@@ -488,7 +513,7 @@ proc checkAttestation*(
 
   true
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#prepare_validator_for_withdrawal
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#prepare_validator_for_withdrawal
 func prepare_validator_for_withdrawal*(state: var BeaconState, index: ValidatorIndex) =
   ## Set the validator with the given ``index`` as withdrawable
   ## ``MIN_VALIDATOR_WITHDRAWABILITY_DELAY`` after the current epoch.
@@ -511,7 +536,7 @@ proc makeAttestationData*(
     epoch_boundary_root =
       if epoch_start_slot == state.slot: beacon_block_root
       else: get_block_root(state, epoch_start_slot)
-    justified_slot = get_epoch_start_slot(state.justified_epoch)
+    justified_slot = get_epoch_start_slot(state.current_justified_epoch)
     justified_block_root = get_block_root(state, justified_slot)
 
   AttestationData(
@@ -521,6 +546,6 @@ proc makeAttestationData*(
     epoch_boundary_root: epoch_boundary_root,
     crosslink_data_root: Eth2Digest(), # Stub in phase0
     latest_crosslink: state.latest_crosslinks[shard],
-    justified_epoch: state.justified_epoch,
+    justified_epoch: state.current_justified_epoch,
     justified_block_root: justified_block_root,
   )
diff --git a/beacon_chain/spec/crypto.nim b/beacon_chain/spec/crypto.nim
index 7dfbf59b1..b98a43329 100644
--- a/beacon_chain/spec/crypto.nim
+++ b/beacon_chain/spec/crypto.nim
@@ -68,7 +68,7 @@ template hash*(k: ValidatorPubKey|ValidatorPrivKey): Hash =
 
 func pubKey*(pk: ValidatorPrivKey): ValidatorPubKey = pk.getKey()
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/bls_signature.md#bls_aggregate_pubkeys
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/bls_signature.md#bls_aggregate_pubkeys
 func bls_aggregate_pubkeys*(keys: openArray[ValidatorPubKey]): ValidatorPubKey =
   var empty = true
   for key in keys:
@@ -78,14 +78,14 @@ func bls_aggregate_pubkeys*(keys: openArray[ValidatorPubKey]): ValidatorPubKey =
     else:
       result.combine(key)
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/bls_signature.md#bls_verify
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/bls_signature.md#bls_verify
 func bls_verify*(
     pubkey: ValidatorPubKey, msg: openArray[byte], sig: ValidatorSig,
     domain: uint64): bool =
   # name from spec!
   sig.verify(msg, domain, pubkey)
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/bls_signature.md#bls_verify_multiple
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/bls_signature.md#bls_verify_multiple
 func bls_verify_multiple*(
     pubkeys: seq[ValidatorPubKey], message_hashes: seq[array[0..31, byte]],
     sig: ValidatorSig, domain: uint64): bool =
diff --git a/beacon_chain/spec/datatypes.nim b/beacon_chain/spec/datatypes.nim
index 3cca0a247..6d1721029 100644
--- a/beacon_chain/spec/datatypes.nim
+++ b/beacon_chain/spec/datatypes.nim
@@ -82,11 +82,11 @@ const
   SHUFFLE_ROUND_COUNT* = 90
 
   # Deposit contract
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#deposit-contract
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#deposit-contract
   DEPOSIT_CONTRACT_TREE_DEPTH* = 2^5
 
   # Gwei values
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#gwei-values
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#gwei-values
   MIN_DEPOSIT_AMOUNT* = 2'u64^0 * 10'u64^9 ##\
   ## Minimum amounth of ETH that can be deposited in one call - deposits can
   ## be used either to top up an existing validator or commit to a new one
@@ -106,8 +106,7 @@ const
   ## processing is done
   ## Compile with -d:SLOTS_PER_EPOCH=4 for shorter epochs
 
-  # Initial values
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#initial-values
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#initial-values
   GENESIS_FORK_VERSION* = 0'u64
   GENESIS_SLOT* = (2'u64^32).Slot
   GENESIS_EPOCH* = (GENESIS_SLOT.uint64 div SLOTS_PER_EPOCH).Epoch ##\
@@ -146,18 +145,18 @@ const
   EPOCHS_PER_ETH1_VOTING_PERIOD* = 2'u64^4 ##\
   ## epochs (~1.7 hours)
 
+  SLOTS_PER_HISTORICAL_ROOT* = 8192 ##\
+  ## slots (13 hours)
+
   MIN_VALIDATOR_WITHDRAWABILITY_DELAY* = 2'u64^8 ##\
   ## epochs (~27 hours)
 
-  # State list lengths
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#state-list-lengths
-  LATEST_BLOCK_ROOTS_LENGTH* = 2'u64^13
-  LATEST_RANDAO_MIXES_LENGTH* = 2'u64^13
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#state-list-lengths
+  LATEST_RANDAO_MIXES_LENGTH* = 8192
   LATEST_ACTIVE_INDEX_ROOTS_LENGTH* = 8192 # 2'u64^13, epochs
   LATEST_SLASHED_EXIT_LENGTH* = 8192 # epochs
 
-  # Reward and penalty quotients
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#reward-and-penalty-quotients
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#reward-and-penalty-quotients
   BASE_REWARD_QUOTIENT* = 2'u64^5 ##\
   ## The `BASE_REWARD_QUOTIENT` parameter dictates the per-epoch reward. It
   ## corresponds to ~2.54% annual interest assuming 10 million participating
@@ -167,8 +166,7 @@ const
   INACTIVITY_PENALTY_QUOTIENT* = 2'u64^24
   MIN_PENALTY_QUOTIENT* = 32 # 2^5
 
-  # Max transactions per block
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#max-transactions-per-block
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#max-transactions-per-block
   MAX_PROPOSER_SLASHINGS* = 2^4
   MAX_ATTESTER_SLASHINGS* = 2^0
   MAX_ATTESTATIONS* = 2^7
@@ -181,16 +179,16 @@ type
 
   Gwei* = uint64
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#proposerslashing
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#proposerslashing
   ProposerSlashing* = object
     proposer_index*: uint64 ##\
     ## Proposer index
 
-    proposal_1*: Proposal ##\
-    # First proposal
+    header_1*: BeaconBlockHeader ##\
+    # First block header
 
-    proposal_2*: Proposal ##\
-    # Second proposal
+    header_2*: BeaconBlockHeader ##\
+    # Second block header
 
   # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#attesterslashing
   AttesterSlashing* = object
@@ -199,7 +197,7 @@ type
     slashable_attestation_2*: SlashableAttestation ## \
     ## Second slashable attestation
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#slashableattestation
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#slashableattestation
   SlashableAttestation* = object
     validator_indices*: seq[uint64] ##\
     ## Validator indices
@@ -253,7 +251,7 @@ type
     justified_block_root*: Eth2Digest ##\
     ## Hash of the last justified beacon block
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#attestationdataandcustodybit
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#attestationdataandcustodybit
   AttestationDataAndCustodyBit* = object
     data*: AttestationData
     custody_bit*: bool
@@ -269,20 +267,20 @@ type
     deposit_data*: DepositData ##\
     ## Data
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#depositdata
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#depositdata
   DepositData* = object
     amount*: uint64 ## Amount in Gwei
     timestamp*: uint64 # Timestamp from deposit contract
     deposit_input*: DepositInput
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#depositinput
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#depositinput
   DepositInput* = object
     pubkey*: ValidatorPubKey
     withdrawal_credentials*: Eth2Digest
     proof_of_possession*: ValidatorSig ##\
     ## A BLS signature of this `DepositInput`
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#voluntaryexit
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#voluntaryexit
   VoluntaryExit* = object
     # Minimum epoch for processing exit
     epoch*: Epoch
@@ -314,7 +312,7 @@ type
     signature*: ValidatorSig ##\
     ## Sender signature
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#beaconblock
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#beaconblock
   BeaconBlock* = object
     ## For each slot, a proposer is chosen from the validator pool to propose
     ## a new block. Once the block as been proposed, it is transmitted to
@@ -323,26 +321,33 @@ type
     ## is formed.
 
     slot*: Slot
-    parent_root*: Eth2Digest ##\
+
+    previous_block_root*: Eth2Digest ##\
     ##\ Root hash of the previous block
 
     state_root*: Eth2Digest ##\
     ## The state root, _after_ this block has been processed
 
-    randao_reveal*: ValidatorSig ##\
-    ## Proposer RANDAO reveal
-
-    eth1_data*: Eth1Data
-
     body*: BeaconBlockBody
 
     signature*: ValidatorSig ##\
     ## Proposer signature
 
+  #https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#beaconblockheader
   BeaconBlockHeader* = object
+    slot*: uint64
+    previous_block_root*: Eth2Digest
+    state_root*: Eth2Digest
+    block_body_root*: Eth2Digest
+    signature*: ValidatorSig
+
+  BeaconBlockHeaderRLP* = object
     ## Same as BeaconBlock, except `body` is the `hash_tree_root` of the
     ## associated BeaconBlockBody.
     # TODO: Dry it up with BeaconBlock
+    # TODO: As a first step, don't change RLP output; only previous user,
+    # but as with others, randao_reveal and eth1_data move to body.
+    # This is from before spec had a version.
     slot*: uint64
     parent_root*: Eth2Digest
     state_root*: Eth2Digest
@@ -351,8 +356,10 @@ type
     signature*: ValidatorSig
     body*: Eth2Digest
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#beaconblockbody
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#beaconblockbody
   BeaconBlockBody* = object
+    randao_reveal*: ValidatorSig
+    eth1_data*: Eth1Data
     proposer_slashings*: seq[ProposerSlashing]
     attester_slashings*: seq[AttesterSlashing]
     attestations*: seq[Attestation]
@@ -374,7 +381,7 @@ type
     signature*: ValidatorSig ##\
     ## Signature
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#beaconstate
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#beaconstate
   BeaconState* = object
     slot*: Slot
     genesis_time*: uint64
@@ -393,7 +400,7 @@ type
     ## For light clients to easily track delta
 
     # Randomness and committees
-    latest_randao_mixes*: array[LATEST_BLOCK_ROOTS_LENGTH.int, Eth2Digest]
+    latest_randao_mixes*: array[LATEST_RANDAO_MIXES_LENGTH, Eth2Digest]
     previous_shuffling_start_shard*: uint64
     current_shuffling_start_shard*: uint64
     previous_shuffling_epoch*: Epoch
@@ -402,20 +409,31 @@ type
     current_shuffling_seed*: Eth2Digest
 
     # Finality
+    previous_epoch_attestations*: seq[PendingAttestation]
+    current_epoch_attestations*: seq[PendingAttestation]
     previous_justified_epoch*: Epoch
-    justified_epoch*: Epoch
+    current_justified_epoch*: Epoch
+    previous_justified_root*: Eth2Digest
+    current_justified_root*: Eth2Digest
     justification_bitfield*: uint64
     finalized_epoch*: Epoch
+    finalized_root*: Eth2Digest
 
     # Recent state
     latest_crosslinks*: array[SHARD_COUNT, Crosslink]
-    latest_block_roots*: array[LATEST_BLOCK_ROOTS_LENGTH.int, Eth2Digest] ##\
+    latest_block_roots*: array[SLOTS_PER_HISTORICAL_ROOT, Eth2Digest] ##\
     ## Needed to process attestations, older to newer
-    latest_active_index_roots*: array[LATEST_ACTIVE_INDEX_ROOTS_LENGTH.int, Eth2Digest]
+    latest_state_roots*: array[SLOTS_PER_HISTORICAL_ROOT, Eth2Digest]
+    latest_active_index_roots*: array[LATEST_ACTIVE_INDEX_ROOTS_LENGTH, Eth2Digest]
 
     latest_slashed_balances*: array[LATEST_SLASHED_EXIT_LENGTH, uint64] ##\
     ## Balances penalized in the current withdrawal period
 
+    latest_block_header*: BeaconBlockHeader ##\
+    ## `latest_block_header.state_root == ZERO_HASH` temporarily
+    historical_roots*: seq[Eth2Digest]
+
+    # TOOD remove these, gone in 0.5
     latest_attestations*: seq[PendingAttestation]
     batched_block_roots*: seq[Eth2Digest]
 
@@ -427,7 +445,7 @@ type
     # Not in spec. TODO: don't serialize or deserialize this.
     shuffling_cache*: ShufflingCache
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#validator
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#validator
   Validator* = object
     pubkey*: ValidatorPubKey ##\
     ## BLS public key
@@ -450,7 +468,7 @@ type
     slashed*: bool ##\
     ## Was the validator slashed
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#crosslink
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#crosslink
   Crosslink* = object
     epoch*: Epoch ##\
     ## Epoch number
@@ -458,20 +476,20 @@ type
     crosslink_data_root*: Eth2Digest ##\
     ## Shard data since the previous crosslink
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#pendingattestation
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#pendingattestation
   PendingAttestation* = object
     aggregation_bitfield*: seq[byte]          # Attester participation bitfield
     data*: AttestationData                    # Attestation data
     custody_bitfield*: seq[byte]              # Custody bitfield
     inclusion_slot*: Slot                     # Inclusion slot
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#fork
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#fork
   Fork* = object
     previous_version*: uint64                     # Previous fork version
     current_version*: uint64                      # Current fork version
     epoch*: Epoch                                 # Fork epoch number
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#eth1data
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#eth1data
   Eth1Data* = object
     deposit_root*: Eth2Digest ##\
     ## Data being voted for
@@ -479,7 +497,7 @@ type
     block_hash*: Eth2Digest ##\
     ## Block hash
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#eth1datavote
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#eth1datavote
   Eth1DataVote* = object
     eth1_data*: Eth1Data ##\
     ## Data being voted for
@@ -493,13 +511,13 @@ type
     Activation = 0
     Exit = 1
 
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#signature-domains
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#signature-domains
   SignatureDomain* {.pure.} = enum
-    DOMAIN_DEPOSIT = 0
-    DOMAIN_ATTESTATION = 1
-    DOMAIN_PROPOSAL = 2
-    DOMAIN_EXIT = 3
-    DOMAIN_RANDAO = 4
+    DOMAIN_BEACON_BLOCK = 0
+    DOMAIN_RANDAO = 1
+    DOMAIN_ATTESTATION = 2
+    DOMAIN_DEPOSIT = 3
+    DOMAIN_VOLUNTARY_EXIT = 4
     DOMAIN_TRANSFER = 5
 
   # TODO: not in spec
@@ -578,8 +596,8 @@ func humaneEpochNum*(e: Epoch): uint64 =
   e - GENESIS_EPOCH
 
 func shortLog*(v: BeaconBlock): tuple[
-    slot: uint64, parent_root: string, state_root: string,
-    randao_reveal: string, #[ eth1_data ]#
+    slot: uint64, previous_block_root: string, state_root: string,
+    #[ eth1_data ]#
     proposer_slashings_len: int, attester_slashings_len: int,
     attestations_len: int,
     deposits_len: int,
@@ -587,8 +605,8 @@ func shortLog*(v: BeaconBlock): tuple[
     transfers_len: int,
     signature: string
   ] = (
-    humaneSlotNum(v.slot), shortLog(v.parent_root), shortLog(v.state_root),
-    shortLog(v.randao_reveal), v.body.proposer_slashings.len(),
+    humaneSlotNum(v.slot), shortLog(v.previous_block_root),
+    shortLog(v.state_root), v.body.proposer_slashings.len(),
     v.body.attester_slashings.len(), v.body.attestations.len(),
     v.body.deposits.len(), v.body.voluntary_exits.len(), v.body.transfers.len(),
     shortLog(v.signature)
diff --git a/beacon_chain/spec/digest.nim b/beacon_chain/spec/digest.nim
index 4ec1b0fbe..48260341b 100644
--- a/beacon_chain/spec/digest.nim
+++ b/beacon_chain/spec/digest.nim
@@ -7,7 +7,7 @@
 
 # Serenity hash function / digest
 #
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#hash
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#hash
 #
 # In Phase 0 the beacon chain is deployed with the same hash function as
 # Ethereum 1.0, i.e. Keccak-256 (also incorrectly known as SHA3).
diff --git a/beacon_chain/spec/helpers.nim b/beacon_chain/spec/helpers.nim
index 3cfaca548..a02d2deef 100644
--- a/beacon_chain/spec/helpers.nim
+++ b/beacon_chain/spec/helpers.nim
@@ -14,14 +14,14 @@ import ./datatypes, ./digest, sequtils, math
 func bitSet*(bitfield: var openArray[byte], index: int) =
   bitfield[index div 8] = bitfield[index div 8] or 1'u8 shl (7 - (index mod 8))
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_bitfield_bit
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_bitfield_bit
 func get_bitfield_bit*(bitfield: openarray[byte], i: int): byte =
   # Extract the bit in ``bitfield`` at position ``i``.
   doAssert 0 <= i div 8, "i: " & $i & " i div 8: " & $(i div 8)
   doAssert i div 8 < bitfield.len, "i: " & $i & " i div 8: " & $(i div 8)
   (bitfield[i div 8] shr (7 - (i mod 8))) mod 2
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#verify_bitfield
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#verify_bitfield
 func verify_bitfield*(bitfield: openarray[byte], committee_size: int): bool =
   # Verify ``bitfield`` against the ``committee_size``.
   if len(bitfield) != (committee_size + 7) div 8:
@@ -34,7 +34,7 @@ func verify_bitfield*(bitfield: openarray[byte], committee_size: int): bool =
 
   true
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#split
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#split
 func split*[T](lst: openArray[T], N: Positive): seq[seq[T]] =
   ## split lst in N pieces, with each piece having `len(lst) div N` or
   ## `len(lst) div N + 1` pieces
@@ -56,9 +56,11 @@ func get_new_recent_block_roots*(old_block_roots: seq[Eth2Digest],
 
 func ceil_div8*(v: int): int = (v + 7) div 8 # TODO use a proper bitarray!
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#integer_squareroot
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#integer_squareroot
 func integer_squareroot*(n: SomeInteger): SomeInteger =
   ## The largest integer ``x`` such that ``x**2`` is less than ``n``.
+  doAssert n >= 0'u64
+
   var
     x = n
     y = (x + 1) div 2
@@ -81,8 +83,8 @@ func get_domain*(
   # Get the domain number that represents the fork meta and signature domain.
   (get_fork_version(fork, epoch) shl 32) + domain_type.uint32
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#is_power_of_two
-func is_power_of_2*(v: uint64): bool = (v and (v-1)) == 0
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#is_power_of_two
+func is_power_of_2*(v: uint64): bool = (v > 0'u64) and (v and (v-1)) == 0
 
 # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#merkle_root
 func merkle_root*(values: openArray[Eth2Digest]): Eth2Digest =
@@ -119,16 +121,16 @@ func merkle_root*(values: openArray[Eth2Digest]): Eth2Digest =
 
   o[1]
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#slot_to_epoch
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#slot_to_epoch
 func slot_to_epoch*(slot: Slot|uint64): Epoch =
   (slot div SLOTS_PER_EPOCH).Epoch
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_epoch_start_slot
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_epoch_start_slot
 func get_epoch_start_slot*(epoch: Epoch): Slot =
   # Return the starting slot of the given ``epoch``.
   (epoch * SLOTS_PER_EPOCH).Slot
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#is_double_vote
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#is_double_vote
 func is_double_vote*(attestation_data_1: AttestationData,
                      attestation_data_2: AttestationData): bool =
   ## Check if ``attestation_data_1`` and ``attestation_data_2`` have the same
@@ -139,7 +141,7 @@ func is_double_vote*(attestation_data_1: AttestationData,
     target_epoch_2 = slot_to_epoch(attestation_data_2.slot)
   target_epoch_1 == target_epoch_2
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#is_surround_vote
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#is_surround_vote
 func is_surround_vote*(attestation_data_1: AttestationData,
                        attestation_data_2: AttestationData): bool =
   ## Check if ``attestation_data_1`` surrounds ``attestation_data_2``.
@@ -152,7 +154,7 @@ func is_surround_vote*(attestation_data_1: AttestationData,
 
   source_epoch_1 < source_epoch_2 and target_epoch_2 < target_epoch_1
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#is_active_validator
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#is_active_validator
 func is_active_validator*(validator: Validator, epoch: Epoch): bool =
   ### Check if ``validator`` is active
   validator.activation_epoch <= epoch and epoch < validator.exit_epoch
@@ -170,7 +172,7 @@ func get_epoch_committee_count*(active_validator_count: int): uint64 =
     active_validator_count div SLOTS_PER_EPOCH div TARGET_COMMITTEE_SIZE,
     1, SHARD_COUNT div SLOTS_PER_EPOCH).uint64 * SLOTS_PER_EPOCH
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_current_epoch_committee_count
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_current_epoch_committee_count
 func get_current_epoch_committee_count*(state: BeaconState): uint64 =
   # Return the number of committees in the current epoch of the given ``state``.
   let current_active_validators = get_active_validator_indices(
@@ -179,13 +181,13 @@ func get_current_epoch_committee_count*(state: BeaconState): uint64 =
   )
   get_epoch_committee_count(len(current_active_validators))
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_current_epoch
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_current_epoch
 func get_current_epoch*(state: BeaconState): Epoch =
   # Return the current epoch of the given ``state``.
   doAssert state.slot >= GENESIS_SLOT, $state.slot
   slot_to_epoch(state.slot)
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_randao_mix
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_randao_mix
 func get_randao_mix*(state: BeaconState,
                      epoch: Epoch): Eth2Digest =
     ## Returns the randao mix at a recent ``epoch``.
@@ -196,7 +198,7 @@ func get_randao_mix*(state: BeaconState,
 
     state.latest_randao_mixes[epoch mod LATEST_RANDAO_MIXES_LENGTH]
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_active_index_root
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_active_index_root
 func get_active_index_root(state: BeaconState, epoch: Epoch): Eth2Digest =
   # Returns the index root at a recent ``epoch``.
 
@@ -216,7 +218,7 @@ func bytes_to_int*(data: seq[byte]): uint64 =
   for i in countdown(7, 0):
     result = result * 256 + data[i]
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#int_to_bytes1-int_to_bytes2-
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#int_to_bytes1-int_to_bytes2-
 # Have 1, 4, and 32-byte versions. 2+ more and maybe worth metaprogramming.
 func int_to_bytes32*(x: uint64): array[32, byte] =
   ## Little-endian data representation
@@ -242,7 +244,7 @@ func int_to_bytes4*(x: uint64): array[4, byte] =
   result[2] = ((x shr 16) and 0xff).byte
   result[3] = ((x shr 24) and 0xff).byte
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#generate_seed
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#generate_seed
 func generate_seed*(state: BeaconState, epoch: Epoch): Eth2Digest =
   # Generate a seed for the given ``epoch``.
 
diff --git a/beacon_chain/spec/validator.nim b/beacon_chain/spec/validator.nim
index 7ba3f200e..040ff77f5 100644
--- a/beacon_chain/spec/validator.nim
+++ b/beacon_chain/spec/validator.nim
@@ -103,7 +103,7 @@ func get_shuffling*(seed: Eth2Digest,
   result = split(shuffled_seq, committees_per_epoch)
   doAssert result.len() == committees_per_epoch # what split should do..
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_previous_epoch_committee_count
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_previous_epoch_committee_count
 func get_previous_epoch_committee_count(state: BeaconState): uint64 =
   ## Return the number of committees in the previous epoch of the given
   ## ``state``.
@@ -113,7 +113,7 @@ func get_previous_epoch_committee_count(state: BeaconState): uint64 =
   )
   get_epoch_committee_count(len(previous_active_validators))
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_next_epoch_committee_count
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_next_epoch_committee_count
 func get_next_epoch_committee_count(state: BeaconState): uint64 =
   ## Return the number of committees in the next epoch of the given ``state``.
   let next_active_validators = get_active_validator_indices(
@@ -140,8 +140,6 @@ func get_crosslink_committees_at_slot*(state: BeaconState, slot: Slot|uint64,
     # TODO: the + 1 here works around a bug, remove when upgrading to
     #       some more recent version:
     # https://github.com/ethereum/eth2.0-specs/pull/732
-    # It's not 100% clear to me regarding 0.4.0; waiting until 0.5.0 to remove
-    # TODO recheck
     epoch = slot_to_epoch(slot + 1)
     current_epoch = get_current_epoch(state)
     previous_epoch = get_previous_epoch(state)
@@ -217,7 +215,7 @@ func get_crosslink_committees_at_slot*(state: BeaconState, slot: Slot|uint64,
      (slot_start_shard + i.uint64) mod SHARD_COUNT
     )
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#get_beacon_proposer_index
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#get_beacon_proposer_index
 func get_beacon_proposer_index*(state: BeaconState, slot: Slot): ValidatorIndex =
   ## From Casper RPJ mini-spec:
   ## When slot i begins, validator Vidx is expected
@@ -232,6 +230,15 @@ func get_beacon_proposer_index*(state: BeaconState, slot: Slot): ValidatorIndex
   #      because presently, `state.slot += 1` happens before this function
   #      is called - see also testutil.getNextBeaconProposerIndex
   # TODO is the above still true? the shuffling has changed since it was written
+  let
+    epoch = slot_to_epoch(slot)
+    current_epoch = get_current_epoch(state)
+    previous_epoch = get_previous_epoch(state)
+    next_epoch = current_epoch + 1
+
+  doAssert previous_epoch <= epoch
+  doAssert epoch <= next_epoch
+
   let (first_committee, _) = get_crosslink_committees_at_slot(state, slot)[0]
   let idx = int(slot mod uint64(first_committee.len))
   first_committee[idx]
diff --git a/beacon_chain/ssz.nim b/beacon_chain/ssz.nim
index d3ac75ce2..9b9e085ce 100644
--- a/beacon_chain/ssz.nim
+++ b/beacon_chain/ssz.nim
@@ -315,14 +315,15 @@ func hash_tree_root*[T: object|tuple](x: T): array[32, byte] =
       h.update hash_tree_root(field.toSSZType)
 
 # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/simple-serialize.md#signed-roots
-func signed_root*[T: object](x: T, field_name: string): array[32, byte] =
+func signed_root*[T: object](x: T, ignored: string = "sig"): array[32, byte] =
   # TODO write tests for this (check vs hash_tree_root)
 
   var found_field_name = false
 
+  ## TODO this isn't how 0.5 defines signed_root, but works well enough
   withHash:
     for name, field in x.fieldPairs:
-      if name == field_name:
+      if name == "signature":
         found_field_name = true
         break
       h.update hash_tree_root(field.toSSZType)
diff --git a/beacon_chain/state_transition.nim b/beacon_chain/state_transition.nim
index a750d7a19..876acc396 100644
--- a/beacon_chain/state_transition.nim
+++ b/beacon_chain/state_transition.nim
@@ -57,9 +57,44 @@ func verifyBlockSignature(state: BeaconState, blck: BeaconBlock): bool =
     proposer.pubkey,
     signed_root(proposal, "signature"),
     proposal.signature,
-    get_domain(state.fork, get_current_epoch(state), DOMAIN_PROPOSAL))
+    get_domain(state.fork, get_current_epoch(state), DOMAIN_BEACON_BLOCK))
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#randao
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#block-header
+proc processBlockHeader(
+    state: var BeaconState, blck: BeaconBlock, flags: UpdateFlags): bool =
+  # Verify that the slots match
+  if not (blck.slot == state.slot):
+    notice "Block header: slot mismatch",
+      block_slot = humaneSlotNum(blck.slot),
+      state_slot = humaneSlotNum(state.slot)
+    return false
+
+  if not (blck.previous_block_root ==
+      hash_tree_root_final(state.latest_block_header)):
+    notice "Block header: previous block root mismatch",
+      previous_block_root = blck.previous_block_root,
+      latest_block_header = state.latest_block_header,
+      latest_block_header_root = hash_tree_root_final(state.latest_block_header)
+    return false
+
+  state.latest_block_header = get_temporary_block_header(blck)
+
+  let proposer =
+    state.validator_registry[get_beacon_proposer_index(state, state.slot)]
+  if skipValidation notin flags and not bls_verify(
+      proposer.pubkey,
+      signed_root(blck),
+      blck.signature,
+      get_domain(state.fork, get_current_epoch(state), DOMAIN_BEACON_BLOCK)):
+    notice "Block header: invalid block header",
+      proposer_pubkey = proposer.pubkey,
+      signed_root_block = signed_root(blck),
+      block_signature = blck.signature
+    return false
+
+  true
+
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#randao
 proc processRandao(
     state: var BeaconState, blck: BeaconBlock, flags: UpdateFlags): bool =
   let
@@ -70,20 +105,21 @@ proc processRandao(
     if not bls_verify(
       proposer.pubkey,
       hash_tree_root(get_current_epoch(state).uint64),
-      blck.randao_reveal,
+      blck.body.randao_reveal,
       get_domain(state.fork, get_current_epoch(state), DOMAIN_RANDAO)):
 
       notice "Randao mismatch", proposer_pubkey = proposer.pubkey,
                                 message = get_current_epoch(state),
-                                signature = blck.randao_reveal,
+                                signature = blck.body.randao_reveal,
                                 slot = state.slot,
                                 blck_slot = blck.slot
       return false
 
-  # Update state and proposer now that we're alright
+  # Mix it in
   let
     mix = get_current_epoch(state) mod LATEST_RANDAO_MIXES_LENGTH
-    rr = hash_tree_root_final(blck.randao_reveal).data
+    # TODO hash_tree_root has some overloading for this
+    rr = eth2hash(blck.body.randao_reveal.getBytes()).data
 
   for i, b in state.latest_randao_mixes[mix].data:
     state.latest_randao_mixes[mix].data[i] = b xor rr[i]
@@ -94,16 +130,16 @@ proc processRandao(
 func processDepositRoot(state: var BeaconState, blck: BeaconBlock) =
   # TODO verify that there's at most one match
   for x in state.eth1_data_votes.mitems():
-    if blck.eth1_data == x.eth1_data:
+    if blck.body.eth1_data == x.eth1_data:
       x.vote_count += 1
       return
 
   state.eth1_data_votes.add Eth1DataVote(
-    eth1_data: blck.eth1_data,
+    eth1_data: blck.body.eth1_data,
     vote_count: 1
   )
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#proposer-slashings-1
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#proposer-slashings
 proc processProposerSlashings(
     state: var BeaconState, blck: BeaconBlock, flags: UpdateFlags): bool =
   if len(blck.body.proposer_slashings) > MAX_PROPOSER_SLASHINGS:
@@ -114,19 +150,13 @@ proc processProposerSlashings(
   for proposer_slashing in blck.body.proposer_slashings:
     let proposer = state.validator_registry[proposer_slashing.proposer_index.int]
 
-    if not (proposer_slashing.proposal_1.slot ==
-        proposer_slashing.proposal_2.slot):
-      notice "PropSlash: slot mismatch"
+    if not (slot_to_epoch(proposer_slashing.header_1.slot) ==
+        slot_to_epoch(proposer_slashing.header_2.slot)):
+      notice "PropSlash: epoch mismatch"
       return false
 
-    if not (proposer_slashing.proposal_1.shard ==
-        proposer_slashing.proposal_2.shard):
-      notice "PropSlash: shard mismatch"
-      return false
-
-    if not (proposer_slashing.proposal_1.block_root !=
-        proposer_slashing.proposal_2.block_root):
-      notice "PropSlash: block root mismatch"
+    if not (proposer_slashing.header_1 != proposer_slashing.header_2):
+      notice "PropSlash: headers not different"
       return false
 
     if not (proposer.slashed == false):
@@ -134,24 +164,16 @@ proc processProposerSlashings(
       return false
 
     if skipValidation notin flags:
-      if not bls_verify(
-          proposer.pubkey,
-          signed_root(proposer_slashing.proposal_1, "signature"),
-          proposer_slashing.proposal_1.signature,
-          get_domain(
-            state.fork, slot_to_epoch(proposer_slashing.proposal_1.slot),
-            DOMAIN_PROPOSAL)):
-        notice "PropSlash: invalid signature 1"
-        return false
-      if not bls_verify(
-          proposer.pubkey,
-          signed_root(proposer_slashing.proposal_2, "signature"),
-          proposer_slashing.proposal_2.signature,
-          get_domain(
-            state.fork, slot_to_epoch(proposer_slashing.proposal_2.slot),
-            DOMAIN_PROPOSAL)):
-        notice "PropSlash: invalid signature 2"
-        return false
+      for i, header in @[proposer_slashing.header_1, proposer_slashing.header_2]:
+        if not bls_verify(
+            proposer.pubkey,
+            signed_root(header),
+            header.signature,
+            get_domain(
+              state.fork, slot_to_epoch(header.slot), DOMAIN_BEACON_BLOCK)):
+          notice "PropSlash: invalid signature",
+            signature_index = i
+          return false
 
     slashValidator(state, proposer_slashing.proposer_index.ValidatorIndex)
 
@@ -303,8 +325,8 @@ proc processExits(
 
     if skipValidation notin flags:
       if not bls_verify(
-          validator.pubkey, signed_root(exit, "signature"), exit.signature,
-          get_domain(state.fork, exit.epoch, DOMAIN_EXIT)):
+          validator.pubkey, signed_root(exit), exit.signature,
+          get_domain(state.fork, exit.epoch, DOMAIN_VOLUNTARY_EXIT)):
         notice "Exit: invalid signature"
         return false
 
@@ -357,7 +379,7 @@ proc processTransfers(state: var BeaconState, blck: BeaconBlock,
       return false
 
     if skipValidation notin flags:
-      let transfer_message = signed_root(transfer, "signature")
+      let transfer_message = signed_root(transfer)
       if not bls_verify(
           pubkey=transfer.pubkey, transfer_message, transfer.signature,
           get_domain(
@@ -375,20 +397,41 @@ proc processTransfers(state: var BeaconState, blck: BeaconBlock,
 
   true
 
-# https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#per-slot-processing
-func processSlot(state: var BeaconState, previous_block_root: Eth2Digest) =
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#per-slot-processing
+func advanceSlot(state: var BeaconState) =
   ## Time on the beacon chain moves in slots. Every time we make it to a new
   ## slot, a proposer creates a block to represent the state of the beacon
   ## chain at that time. In case the proposer is missing, it may happen that
   ## the no block is produced during the slot.
-
-  # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#slot
   state.slot += 1
 
+# https://github.com/ethereum/eth2.0-specs/blob/v0.5.0/specs/core/0_beacon-chain.md#state-caching
+func cacheState(state: var BeaconState) =
+  let previous_slot_state_root = hash_tree_root_final(state)
+
+  # store the previous slot's post state transition root
+  state.latest_state_roots[state.slot mod SLOTS_PER_HISTORICAL_ROOT] =
+    previous_slot_state_root
+
+  # cache state root in stored latest_block_header if empty
+  if state.latest_block_header.state_root == ZERO_HASH:
+    state.latest_block_header.state_root = previous_slot_state_root
+
+  # store latest known block for previous slot
+  state.latest_block_roots[state.slot mod SLOTS_PER_HISTORICAL_ROOT] =
+    hash_tree_root_final(state.latest_block_header)
+
+func processSlot(state: var BeaconState, previous_block_root: Eth2Digest) =
+  advanceSlot(state)
+
+  # TODO "at every slot > GENESIS_SLOT", after rest of epoch restructuring
+  if false and state.slot > GENESIS_SLOT:
+    cacheState(state)
+
   # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#block-roots
-  state.latest_block_roots[(state.slot - 1) mod LATEST_BLOCK_ROOTS_LENGTH] =
+  state.latest_block_roots[(state.slot - 1) mod SLOTS_PER_HISTORICAL_ROOT] =
     previous_block_root
-  if state.slot mod LATEST_BLOCK_ROOTS_LENGTH == 0:
+  if state.slot mod SLOTS_PER_HISTORICAL_ROOT == 0:
     state.batched_block_roots.add(merkle_root(state.latest_block_roots))
 
 proc processBlock(
@@ -408,21 +451,26 @@ proc processBlock(
 
   # Spec does not have this check explicitly, but requires that this condition
   # holds - so we give verify it as well - this would happen naturally if
-  # `blck.parent_root` was used in `processSlot` - but that doesn't cut it for
+  # `blck.previous_block_root` was used in `processSlot` - but that doesn't cut it for
   # blockless slot processing.
+  # TODO compare with check in processBlockHeader, might be redundant
   let stateParentRoot =
-    state.latest_block_roots[(state.slot - 1) mod LATEST_BLOCK_ROOTS_LENGTH]
-  if not (blck.parent_root == stateParentRoot):
+    state.latest_block_roots[(state.slot - 1) mod SLOTS_PER_HISTORICAL_ROOT]
+  if not (blck.previous_block_root == stateParentRoot):
     notice "Unexpected parent root",
-      blockParentRoot = blck.parent_root,
+      blockParentRoot = blck.previous_block_root,
       stateParentRoot
     return false
 
+  # TODO Technically, we could make processBlock take a generic type instead
+  #      of BeaconBlock - we would then have an intermediate `ProposedBlock`
+  #      type that omits some fields - this way, the compiler would guarantee
+  #      that we don't try to access fields that don't have a value yet
+  #if not processBlockHeader(state, blck, flags):
+  #  notice "Block header not valid", slot = humaneSlotNum(state.slot)
+  #  return false
+  # TODO this starts requiring refactoring blockpool, etc
   if skipValidation notin flags:
-    # TODO Technically, we could make processBlock take a generic type instead
-    #      of BeaconBlock - we would then have an intermediate `ProposedBlock`
-    #      type that omits some fields - this way, the compiler would guarantee
-    #      that we don't try to access fields that don't have a value yet
     if not verifyBlockSignature(state, blck):
       notice "Block signature not valid", slot = humaneSlotNum(state.slot)
       return false
@@ -683,7 +731,7 @@ func processEpoch(state: var BeaconState) =
   # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#justification
   block:
     # First, update the justification bitfield
-    var new_justified_epoch = state.justified_epoch
+    var new_justified_epoch = state.current_justified_epoch
     state.justification_bitfield = state.justification_bitfield shl 1
     if 3'u64 * previous_epoch_boundary_attesting_balance >= 2'u64 * previous_total_balance:
       state.justification_bitfield = state.justification_bitfield or 2
@@ -697,14 +745,14 @@ func processEpoch(state: var BeaconState) =
       state.finalized_epoch = state.previous_justified_epoch
     if (state.justification_bitfield shr 1) mod 4 == 0b11 and state.previous_justified_epoch == previous_epoch - 1:
       state.finalized_epoch = state.previous_justified_epoch
-    if (state.justification_bitfield shr 0) mod 8 == 0b111 and state.justified_epoch == previous_epoch - 1:
-      state.finalized_epoch = state.justified_epoch
-    if (state.justification_bitfield shr 0) mod 4 == 0b11 and state.justified_epoch == previous_epoch:
-      state.finalized_epoch = state.justified_epoch
+    if (state.justification_bitfield shr 0) mod 8 == 0b111 and state.current_justified_epoch == previous_epoch - 1:
+      state.finalized_epoch = state.current_justified_epoch
+    if (state.justification_bitfield shr 0) mod 4 == 0b11 and state.current_justified_epoch == previous_epoch:
+      state.finalized_epoch = state.current_justified_epoch
 
     # Finally, update the following
-    state.previous_justified_epoch = state.justified_epoch
-    state.justified_epoch = new_justified_epoch
+    state.previous_justified_epoch = state.current_justified_epoch
+    state.current_justified_epoch = new_justified_epoch
 
   # https://github.com/ethereum/eth2.0-specs/blob/0.4.0/specs/core/0_beacon-chain.md#crosslinks
   block:
diff --git a/beacon_chain/sync_protocol.nim b/beacon_chain/sync_protocol.nim
index ec3ce3bd3..bc8143f11 100644
--- a/beacon_chain/sync_protocol.nim
+++ b/beacon_chain/sync_protocol.nim
@@ -22,30 +22,30 @@ type
     node*: BeaconNode
     db*: BeaconChainDB
 
-func toHeader(b: BeaconBlock): BeaconBlockHeader =
-  BeaconBlockHeader(
+func toHeader(b: BeaconBlock): BeaconBlockHeaderRLP =
+  BeaconBlockHeaderRLP(
     slot: b.slot.uint64,
-    parent_root: b.parent_root,
+    parent_root: b.previous_block_root,
     state_root: b.state_root,
-    randao_reveal: b.randao_reveal,
-    eth1_data : b.eth1_data,
+    randao_reveal: b.body.randao_reveal,
+    eth1_data : b.body.eth1_data,
     signature: b.signature,
     body: hash_tree_root_final(b.body)
   )
 
-proc fromHeaderAndBody(b: var BeaconBlock, h: BeaconBlockHeader, body: BeaconBlockBody) =
+proc fromHeaderAndBody(b: var BeaconBlock, h: BeaconBlockHeaderRLP, body: BeaconBlockBody) =
   doAssert(hash_tree_root_final(body) == h.body)
   b.slot = h.slot.Slot
-  b.parent_root = h.parent_root
+  b.previous_block_root = h.parent_root
   b.state_root = h.state_root
-  b.randao_reveal = h.randao_reveal
-  b.eth1_data = h.eth1_data
+  b.body.randao_reveal = h.randao_reveal
+  b.body.eth1_data = h.eth1_data
   b.signature = h.signature
   b.body = body
 
 proc importBlocks(node: BeaconNode,
                   roots: openarray[(Eth2Digest, Slot)],
-                  headers: openarray[BeaconBlockHeader],
+                  headers: openarray[BeaconBlockHeaderRLP],
                   bodies: openarray[BeaconBlockBody]) =
   var bodyMap = initTable[Eth2Digest, int]()
 
@@ -135,7 +135,7 @@ p2pProtocol BeaconSync(version = 1,
             skipSlots: int) {.libp2pProtocol("rpc/beacon_block_headers", "1.0.0").} =
       # TODO: validate maxHeaders and implement slipSlots
       var s = slot.int
-      var headers = newSeqOfCap[BeaconBlockHeader](maxHeaders)
+      var headers = newSeqOfCap[BeaconBlockHeaderRLP](maxHeaders)
       let db = peer.networkState.db
       let blockPool = peer.networkState.node.blockPool
       while headers.len < maxHeaders:
@@ -147,7 +147,7 @@ p2pProtocol BeaconSync(version = 1,
 
     proc beaconBlockHeaders(
             peer: Peer,
-            blockHeaders: openarray[BeaconBlockHeader])
+            blockHeaders: openarray[BeaconBlockHeaderRLP])
 
   requestResponse:
     proc getBeaconBlockBodies(
diff --git a/beacon_chain/validator_pool.nim b/beacon_chain/validator_pool.nim
index 4de4133a8..46d493202 100644
--- a/beacon_chain/validator_pool.nim
+++ b/beacon_chain/validator_pool.nim
@@ -31,7 +31,7 @@ proc signBlockProposal*(v: AttachedValidator, fork: Fork,
     let proposalRoot = hash_tree_root_final(proposal)
 
     result = bls_sign(v.privKey, signed_root(proposal, "signature"),
-      get_domain(fork, slot_to_epoch(proposal.slot), DOMAIN_PROPOSAL))
+      get_domain(fork, slot_to_epoch(proposal.slot), DOMAIN_BEACON_BLOCK))
   else:
     # TODO:
     # send RPC
diff --git a/research/fork_choice_rule/lmd_ghost.nim b/research/fork_choice_rule/lmd_ghost.nim
index ec392f66d..3ba303bec 100644
--- a/research/fork_choice_rule/lmd_ghost.nim
+++ b/research/fork_choice_rule/lmd_ghost.nim
@@ -56,7 +56,7 @@ func hash(x: BlockHash): Hash =
   result = cast[array[num_hashes, Hash]](x)[0]
 
 func get_parent(store: Store, blck: BeaconBlock): BeaconBlock =
-  store.verified_blocks[blck.parent_root]
+  store.verified_blocks[blck.previous_block_root]
 
 func get_ancestor(store: Store, blck: BeaconBlock, slot: uint64): BeaconBlock =
   ## Find the ancestor with a specific slot number
diff --git a/tests/test_beacon_chain_db.nim b/tests/test_beacon_chain_db.nim
index 609de1105..bf975a950 100644
--- a/tests/test_beacon_chain_db.nim
+++ b/tests/test_beacon_chain_db.nim
@@ -57,12 +57,11 @@ suite "Beacon chain DB":
     check: x == y
 
     let
-      # TODO Not GENESIS_SLOT?
-      a0 = BeaconBlock(slot: 0.Slot)
+      a0 = BeaconBlock(slot: GENESIS_SLOT + 0)
       a0r = hash_tree_root_final(a0)
-      a1 = BeaconBlock(slot: 1.Slot, parent_root: a0r)
+      a1 = BeaconBlock(slot: GENESIS_SLOT + 1, previous_block_root: a0r)
       a1r = hash_tree_root_final(a1)
-      a2 = BeaconBlock(slot: 2.Slot, parent_root: a1r)
+      a2 = BeaconBlock(slot: GENESIS_SLOT + 2, previous_block_root: a1r)
       a2r = hash_tree_root_final(a2)
 
     doAssert toSeq(db.getAncestors(a0r)) == []
diff --git a/tests/testutil.nim b/tests/testutil.nim
index 8d21bb354..abfdec495 100644
--- a/tests/testutil.nim
+++ b/tests/testutil.nim
@@ -92,18 +92,21 @@ proc addBlock*(
     proposer = state.validator_registry[proposer_index]
     privKey = hackPrivKey(proposer)
 
+  # TODO ugly hack; API needs rethinking
+  var new_body = body
+  new_body.randao_reveal = privKey.genRandaoReveal(state, state.slot + 1)
+  new_body.eth1_data = Eth1Data()
+
   var
     # In order to reuse the state transition function, we first create a dummy
     # block that has some fields set, and use that to generate the state as it
     # would look with the new block applied.
     new_block = BeaconBlock(
       slot: state.slot + 1,
-      parent_root: previous_block_root,
+      previous_block_root: previous_block_root,
       state_root: Eth2Digest(), # we need the new state first
-      randao_reveal: privKey.genRandaoReveal(state, state.slot + 1),
-      eth1_data: Eth1Data(), # TODO
       signature: ValidatorSig(), # we need the rest of the block first!
-      body: body
+      body: new_body
     )
 
   let block_ok = updateState(
@@ -134,12 +137,12 @@ proc addBlock*(
     # We have a signature - put it in the block and we should be done!
     new_block.signature =
       bls_sign(proposerPrivkey, proposal_hash,
-               get_domain(state.fork, slot_to_epoch(state.slot), DOMAIN_PROPOSAL))
+               get_domain(state.fork, slot_to_epoch(state.slot), DOMAIN_BEACON_BLOCK))
 
     doAssert bls_verify(
       proposer.pubkey,
       proposal_hash, new_block.signature,
-      get_domain(state.fork, slot_to_epoch(state.slot), DOMAIN_PROPOSAL)),
+      get_domain(state.fork, slot_to_epoch(state.slot), DOMAIN_BEACON_BLOCK)),
       "we just signed this message - it should pass verification!"
 
   new_block