diff --git a/beacon_chain/networking/eth2_network.nim b/beacon_chain/networking/eth2_network.nim
index 6566a213c..d7e6336b1 100644
--- a/beacon_chain/networking/eth2_network.nim
+++ b/beacon_chain/networking/eth2_network.nim
@@ -9,7 +9,7 @@
 
 import
   # Std lib
-  std/[typetraits, sequtils, os, algorithm, math, sets, strutils],
+  std/[typetraits, sequtils, os, algorithm, math, sets],
   std/options as stdOptions,
 
   # Status libs
diff --git a/beacon_chain/spec/datatypes/altair.nim b/beacon_chain/spec/datatypes/altair.nim
index 2a937fb6a..c204267d9 100644
--- a/beacon_chain/spec/datatypes/altair.nim
+++ b/beacon_chain/spec/datatypes/altair.nim
@@ -430,6 +430,8 @@ type
 
   SomeSomeSignedBeaconBlock* = SomeSignedBeaconBlock | phase0.SomeSignedBeaconBlock
 
+  SyncCommitteeIndex* = distinct uint8
+
 # TODO when https://github.com/nim-lang/Nim/issues/14440 lands in Status's Nim,
 # switch proc {.noSideEffect.} to func.
 when false:
@@ -440,6 +442,8 @@ when false:
 
 chronicles.formatIt BeaconBlock: it.shortLog
 
+template asUInt8*(x: SyncCommitteeIndex): uint8 = uint8(x)
+
 Json.useCustomSerialization(BeaconState.justification_bits):
   read:
     let s = reader.readValue(string)
diff --git a/beacon_chain/spec/datatypes/base.nim b/beacon_chain/spec/datatypes/base.nim
index dcf0cc23f..01a30f987 100644
--- a/beacon_chain/spec/datatypes/base.nim
+++ b/beacon_chain/spec/datatypes/base.nim
@@ -678,10 +678,23 @@ func `[]`*[T](a: seq[T], b: ValidatorIndex): auto =
   a[b.int]
 
 # `ValidatorIndex` Nim integration
-proc `==`*(x, y: ValidatorIndex) : bool {.borrow, noSideEffect.}
-proc `<`*(x, y: ValidatorIndex) : bool {.borrow, noSideEffect.}
-proc hash*(x: ValidatorIndex): Hash {.borrow, noSideEffect.}
-func `$`*(x: ValidatorIndex): auto = $(distinctBase(x))
+template `==`*(x, y: ValidatorIndex) : bool =
+  distinctBase(x) == distinctBase(y)
+
+template `<`*(x, y: ValidatorIndex): bool =
+  distinctBase(x) < distinctBase(y)
+
+template hash*(x: ValidatorIndex): Hash =
+  hash distinctBase(x)
+
+template `$`*(x: ValidatorIndex): auto =
+  $ distinctBase(x)
+
+template `==`*(x: uint64, y: ValidatorIndex): bool =
+  x == uint64(y)
+
+template `==`*(x: ValidatorIndex, y: uint64): bool =
+  uint64(x) == y
 
 # TODO Nim 1.4, but not Nim 1.2, defines a function by this name, which works
 # only on openArray[int]. They do the same thing, so either's fine, when both
@@ -692,13 +705,23 @@ func toIntSet*[T](x: openArray[T]): IntSet =
   for item in items(x):
     result.incl(item.int)
 
-proc `==`*(x, y: CommitteeIndex) : bool {.borrow, noSideEffect.}
-proc `<`*(x, y: CommitteeIndex) : bool {.borrow, noSideEffect.}
-proc hash*(x: CommitteeIndex): Hash {.borrow, noSideEffect.}
-func `$`*(x: CommitteeIndex): auto = $(distinctBase(x))
+template `==`*(x, y: CommitteeIndex): bool =
+  distinctBase(x) == distinctBase(y)
 
-proc `==`*(x, y: SubnetId) : bool {.borrow, noSideEffect.}
-proc `$`*(x: SubnetId): string {.borrow, noSideEffect.}
+template `<`*(x, y: CommitteeIndex): bool =
+  distinctBase(x) < distinctBase(y)
+
+template hash*(x: CommitteeIndex): Hash =
+  hash distinctBase(x)
+
+template `$`*(x: CommitteeIndex): auto =
+  $ distinctBase(x)
+
+template `==`*(x, y: SubnetId): bool =
+  distinctBase(x) == distinctBase(y)
+
+template `$`*(x: SubnetId): string =
+  $ distinctBase(x)
 
 func `as`*(d: DepositData, T: type DepositMessage): T =
   T(pubkey: d.pubkey,
@@ -753,7 +776,7 @@ template newClone*[T](x: ref T not nil): ref T =
   newClone(x[])
 
 template lenu64*(x: untyped): untyped =
-  x.len.uint64
+  uint64(len(x))
 
 func `$`*(v: ForkDigest | Version): string =
   toHex(array[4, byte](v))
diff --git a/beacon_chain/spec/network.nim b/beacon_chain/spec/network.nim
index 2d313e37f..d6d10c36e 100644
--- a/beacon_chain/spec/network.nim
+++ b/beacon_chain/spec/network.nim
@@ -79,6 +79,17 @@ func getAttestationTopic*(forkDigest: ForkDigest,
   ## For subscribing and unsubscribing to/from a subnet.
   eth2Prefix(forkDigest) & "beacon_attestation_" & $(subnetId) & "/ssz"
 
+# https://github.com/ethereum/eth2.0-specs/blob/v1.1.0-alpha.8/specs/altair/p2p-interface.md#topics-and-messages
+func getSyncCommitteeTopic*(forkDigest: ForkDigest,
+                            committeeIdx: SyncCommitteeIndex): string =
+  ## For subscribing and unsubscribing to/from a subnet.
+  eth2Prefix(forkDigest) & "sync_committee_" & $(committeeIdx.asUInt8) & "/ssz"
+
+# https://github.com/ethereum/eth2.0-specs/blob/v1.1.0-alpha.8/specs/altair/p2p-interface.md#topics-and-messages
+func getSyncCommitteeContributionAndProofTopic*(forkDigest: ForkDigest): string =
+  ## For subscribing and unsubscribing to/from a subnet.
+  eth2Prefix(forkDigest) & "sync_committee_contribution_and_proof" & "/ssz"
+
 func getENRForkID*(cfg: RuntimeConfig,
                    epoch: Epoch,
                    genesis_validators_root: Eth2Digest): ENRForkID =
diff --git a/ncli/ncli_db.nim b/ncli/ncli_db.nim
index 3c194412f..e7787c87d 100644
--- a/ncli/ncli_db.nim
+++ b/ncli/ncli_db.nim
@@ -514,7 +514,7 @@ proc cmdValidatorPerf(conf: DbConf, cfg: RuntimeConfig) =
               perf.first_slot_head_attester_when_first_slot_not_empty += 1
 
           if s.is_previous_epoch_attester.isSome():
-            perf.delays.mGetOrPut(
+            perf.delays.mgetOrPut(
               s.is_previous_epoch_attester.get().delay, 0'u64) += 1
 
         else:
diff --git a/tests/test_honest_validator.nim b/tests/test_honest_validator.nim
index 767286892..c01d85eaa 100644
--- a/tests/test_honest_validator.nim
+++ b/tests/test_honest_validator.nim
@@ -4,7 +4,7 @@ import
   unittest2,
   ./testutil,
   ../beacon_chain/spec/network,
-  ../beacon_chain/spec/datatypes/base,
+  ../beacon_chain/spec/datatypes/[base, altair],
   ../beacon_chain/validators/attestation_aggregation
 
 suite "Honest validator":
@@ -17,6 +17,7 @@ suite "Honest validator":
       getProposerSlashingsTopic(forkDigest) == "/eth2/00000000/proposer_slashing/ssz"
       getAttesterSlashingsTopic(forkDigest) == "/eth2/00000000/attester_slashing/ssz"
       getAggregateAndProofsTopic(forkDigest) == "/eth2/00000000/beacon_aggregate_and_proof/ssz"
+      getSyncCommitteeContributionAndProofTopic(forkDigest) == "/eth2/00000000/sync_committee_contribution_and_proof/ssz"
 
   test "Mainnet attestation topics":
     check:
@@ -60,6 +61,12 @@ suite "Honest validator":
         "/eth2/00000000/beacon_attestation_62/ssz"
       getAttestationTopic(forkDigest, SubnetId(63)) ==
         "/eth2/00000000/beacon_attestation_63/ssz"
+      getSyncCommitteeTopic(forkDigest, SyncCommitteeIndex(0)) ==
+        "/eth2/00000000/sync_committee_0/ssz"
+      getSyncCommitteeTopic(forkDigest, SyncCommitteeIndex(1)) ==
+        "/eth2/00000000/sync_committee_1/ssz"
+      getSyncCommitteeTopic(forkDigest, SyncCommitteeIndex(3)) ==
+        "/eth2/00000000/sync_committee_3/ssz"
 
   test "is_aggregator":
     check: