diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index d8fb36f4d..0facc0a85 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -1040,7 +1040,7 @@ def get_attestation_participants(state: BeaconState,
 
     assert attestation_data.shard in [shard for _, shard in crosslink_committees]
     crosslink_committee = [committee for committee, shard in crosslink_committees if shard == attestation_data.shard][0]
-    assert len(aggregation_bitfield) == (len(committee) + 7) // 8
+    assert len(aggregation_bitfield) == (len(crosslink_committee) + 7) // 8
 
     # Find the participating attesters in the committee
     participants = []