diff --git a/beacon_node/beacon_chain/test_harness/src/beacon_chain_harness.rs b/beacon_node/beacon_chain/test_harness/src/beacon_chain_harness.rs
index b7acac9e1..33c12d7c7 100644
--- a/beacon_node/beacon_chain/test_harness/src/beacon_chain_harness.rs
+++ b/beacon_node/beacon_chain/test_harness/src/beacon_chain_harness.rs
@@ -178,8 +178,8 @@ impl BeaconChainHarness {
                     agg_sig
                 };
 
-                let mut aggregation_bitfield = Bitfield::with_capacity(committee.committee.len());
-                let custody_bitfield = Bitfield::with_capacity(committee.committee.len());
+                let mut aggregation_bitfield = Bitfield::with_capacity(duties.committee_len);
+                let custody_bitfield = Bitfield::with_capacity(duties.committee_len);
 
                 aggregation_bitfield.set(duties.committee_index, true);