diff --git a/tests/core/pyspec/eth2spec/test/altair/block_processing/sync_aggregate/test_process_sync_aggregate.py b/tests/core/pyspec/eth2spec/test/altair/block_processing/sync_aggregate/test_process_sync_aggregate.py
index 95e0284d2..bd52ce727 100644
--- a/tests/core/pyspec/eth2spec/test/altair/block_processing/sync_aggregate/test_process_sync_aggregate.py
+++ b/tests/core/pyspec/eth2spec/test/altair/block_processing/sync_aggregate/test_process_sync_aggregate.py
@@ -32,7 +32,7 @@ def test_invalid_signature_bad_domain(spec, state):
 
     block = build_empty_block_for_next_slot(spec, state)
     block.body.sync_aggregate = spec.SyncAggregate(
-        sync_committee_bits=committee_indices,
+        sync_committee_bits=[True] * len(committee_indices),
         sync_committee_signature=compute_aggregate_sync_committee_signature(
             spec,
             state,