diff --git a/specs/phase1/shard-fork-choice.md b/specs/phase1/shard-fork-choice.md
index b6d5c5ad4..8d64eb842 100644
--- a/specs/phase1/shard-fork-choice.md
+++ b/specs/phase1/shard-fork-choice.md
@@ -170,7 +170,9 @@ def on_shard_block(store: Store, shard_store: ShardStore, signed_shard_block: Si
 
     # Check the block is valid and compute the post-state
     shard_state = shard_parent_state.copy()
-    shard_state_transition(shard_state, shard_block, validate_message=True, beacon_parent_state=beacon_parent_state)
+    shard_state_transition(
+        shard_state, signed_shard_block,
+        validate=True, beacon_parent_state=beacon_parent_state)
 
     # Add new block to the store
     shard_store.blocks[hash_tree_root(shard_block)] = shard_block
diff --git a/specs/phase1/shard-transition.md b/specs/phase1/shard-transition.md
index e9982b370..05f986000 100644
--- a/specs/phase1/shard-transition.md
+++ b/specs/phase1/shard-transition.md
@@ -50,10 +50,10 @@ def verify_shard_block_message(beacon_parent_state: BeaconState,
 ```
 
 ```python
-def verify_shard_block_signature(beacon_state: BeaconState,
+def verify_shard_block_signature(beacon_parent_state: BeaconState,
                                  signed_block: SignedShardBlock) -> bool:
-    proposer = beacon_state.validators[signed_block.message.proposer_index]
-    domain = get_domain(beacon_state, DOMAIN_SHARD_PROPOSAL, compute_epoch_at_slot(signed_block.message.slot))
+    proposer = beacon_parent_state.validators[signed_block.message.proposer_index]
+    domain = get_domain(beacon_parent_state, DOMAIN_SHARD_PROPOSAL, compute_epoch_at_slot(signed_block.message.slot))
     signing_root = compute_signing_root(signed_block.message, domain)
     return bls.Verify(proposer.pubkey, signing_root, signed_block.signature)
 ```
@@ -62,14 +62,15 @@ def verify_shard_block_signature(beacon_state: BeaconState,
 
 ```python
 def shard_state_transition(shard_state: ShardState,
-                           block: ShardBlock,
-                           validate_message: bool = True,
+                           signed_block: SignedShardBlock,
+                           validate: bool = True,
                            beacon_parent_state: Optional[BeaconState] = None) -> ShardState:
-    if validate_message:
+    if validate:
         assert beacon_parent_state is not None
-        assert verify_shard_block_message(beacon_parent_state, shard_state, block)
+        assert verify_shard_block_message(beacon_parent_state, shard_state, signed_block.message)
+        assert verify_shard_block_signature(beacon_parent_state, signed_block)
 
-    process_shard_block(shard_state, block)
+    process_shard_block(shard_state, signed_block.message)
     return shard_state
 ```
 
@@ -127,7 +128,7 @@ def is_valid_fraud_proof(beacon_state: BeaconState,
     else:
         shard_state = transition.shard_states[offset_index - 1]  # Not doing the actual state updates here.
 
-    shard_state_transition(shard_state, block, validate_message=False)
+    shard_state_transition(shard_state, block, validate=False)
     if shard_state != transition.shard_states[offset_index]:
         return True
 
diff --git a/specs/phase1/validator.md b/specs/phase1/validator.md
index d78726bc2..c0d6ecbf9 100644
--- a/specs/phase1/validator.md
+++ b/specs/phase1/validator.md
@@ -299,7 +299,7 @@ def get_shard_transition_fields(
             shard_block = SignedShardBlock(message=ShardBlock(slot=slot, shard=shard))
             shard_data_roots.append(Root())
         shard_state = shard_state.copy()
-        shard_state_transition(shard_state, shard_block.message, validate_message=False)
+        shard_state_transition(shard_state, shard_block, validate=False)
         shard_states.append(shard_state)
         shard_block_lengths.append(len(shard_block.message.body))