diff --git a/pkg/tasks/check_consensus_attestation_stats/task.go b/pkg/tasks/check_consensus_attestation_stats/task.go
index 89b374c4..b4d7efa5 100644
--- a/pkg/tasks/check_consensus_attestation_stats/task.go
+++ b/pkg/tasks/check_consensus_attestation_stats/task.go
@@ -499,14 +499,19 @@ func (t *Task) aggregateEpochVotes(ctx context.Context, epoch uint64) []*epochVo
 						continue
 					}
 
+					// committeeBits is a bitfield.Bitvector64, whose BitAt only works at
+					// the mainnet 8-byte size; under smaller presets it is shorter, so we
+					// test the bits length-agnostically (see committeeBitSet).
+					committeeBitsBytes := []byte(committeeBits)
+
 					aggregationBitsOffset := uint64(0)
 
 					for committee := uint64(0); committee < specs.MaxCommitteesPerSlot; committee++ {
-						if !committeeBits.BitAt(committee) {
+						if !committeeBitSet(committeeBitsBytes, committee) {
 							continue
 						}
 
-						voteAmt, voteCnt, committeeSize := t.aggregateAttestationVotes(votes, uint64(attData.Slot), committee, attAggregationBits, 0)
+						voteAmt, voteCnt, committeeSize := t.aggregateAttestationVotes(votes, uint64(attData.Slot), committee, attAggregationBits, aggregationBitsOffset)
 						voteAmount += voteAmt
 						voteCount += voteCnt
 						aggregationBitsOffset += committeeSize
@@ -559,6 +564,12 @@ func (t *Task) aggregateEpochVotes(ctx context.Context, epoch uint64) []*epochVo
 	return votes
 }
 
+// committeeBitSet reports whether the committee-th bit is set in b.
+func committeeBitSet(b []byte, committee uint64) bool {
+	byteIdx := committee / 8
+	return byteIdx < uint64(len(b)) && b[byteIdx]&(1<<(committee%8)) != 0
+}
+
 func (t *Task) aggregateAttestationVotes(votes *epochVotes, slot, committee uint64, aggregationBits bitfield.Bitfield, aggregationBitsOffset uint64) (voteAmount, voteCount, validatorCount uint64) {
 	attKey := fmt.Sprintf("%v-%v", slot, committee)
 	voteValidators := votes.attesterDuties.duties[attKey]