diff --git a/tests/test_worker_inbound_transport.py b/tests/test_worker_inbound_transport.py
index 1ee4241b..d1681d35 100644
--- a/tests/test_worker_inbound_transport.py
+++ b/tests/test_worker_inbound_transport.py
@@ -338,6 +338,13 @@ async def test_reconnect_redelivers_an_inbound_result_not_yet_acknowledged(
 async def test_lost_result_ack_refetch_keeps_the_committed_inbound_artifact(
     inbound, monkeypatch
 ):
+    from worker.inbound.artifacts import KeyedArtifactTransport
+    cleanup_done = asyncio.Event()
+    real_cleanup = KeyedArtifactTransport.result_acked_async
+    async def observe_cleanup(transport, artifacts):
+        await real_cleanup(transport, artifacts)
+        cleanup_done.set()
+    monkeypatch.setattr(KeyedArtifactTransport, "result_acked_async", observe_cleanup)
     issued = inbound.keys.issue("Test panel")
     payload = b"rendered audio" * 24_000
 
@@ -395,9 +402,10 @@ async def test_lost_result_ack_refetch_keeps_the_committed_inbound_artifact(
     assert open(committed, "rb").read() == payload
     # The ACK removes the pending item before awaiting filesystem cleanup.
     # Observe completion of that asynchronous operation, not its queue marker.
-    await _until(lambda: inbound.artifacts.open_result(
+    await asyncio.wait_for(cleanup_done.wait(), timeout=5)
+    assert inbound.artifacts.open_result(
         artifact_id, key_id=inbound.panel_key_id
-    ) is None)
+    ) is None
     assert inbound.executed == [task.task_id]