diff --git a/tests/core/pyspec/eth2spec/test/altair/unittests/test_sync_protocol.py b/tests/core/pyspec/eth2spec/test/altair/unittests/test_sync_protocol.py
index a3cf8b7ca..c69957de5 100644
--- a/tests/core/pyspec/eth2spec/test/altair/unittests/test_sync_protocol.py
+++ b/tests/core/pyspec/eth2spec/test/altair/unittests/test_sync_protocol.py
@@ -52,7 +52,7 @@ def test_process_light_client_update_not_updated(spec, state):
     sync_committee_signature = compute_aggregate_sync_committee_signature(
         spec,
         state,
-        block.slot,
+        block_header.slot,
         committee,
     )
     next_sync_committee_branch = [spec.Bytes32() for _ in range(spec.floorlog2(spec.NEXT_SYNC_COMMITTEE_INDEX))]