diff --git a/tests/test_attestation_matrix.py b/tests/test_attestation_matrix.py
index 983d48e..35c7101 100644
--- a/tests/test_attestation_matrix.py
+++ b/tests/test_attestation_matrix.py
@@ -102,9 +102,10 @@ def test_dr_blocks_on_missing_dr_drill():
 
 def test_signature_skip_when_key_unset(monkeypatch, capsys):
     """D-089: signature verification is skipped when the signing key is unset."""
-    # P2: dual-read — both NOVA_* and ACDL_* must be unset for the skip.
+    # P5 (REQ-164): dual-read fallback removed — NOVA_* only. Deleting
+    # NOVA_ATTESTATION_SIGNING_KEY_ID is sufficient for the skip (the
+    # ACDL_* fallback no longer exists in core/env.py).
     monkeypatch.delenv("NOVA_ATTESTATION_SIGNING_KEY_ID", raising=False)
-    monkeypatch.delenv("ACDL_ATTESTATION_SIGNING_KEY_ID", raising=False)
     artifact = {"timestamp": datetime.datetime.now(datetime.timezone.utc).isoformat(),
                 "type": "x", "payload": {}, "signature": "sig"}
     assert _verify_signature(artifact) is True