diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests/Runtime/GalaxyDriverShutdownTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests/Runtime/GalaxyDriverShutdownTests.cs
index 5c2b9b94f..6c2b45481 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests/Runtime/GalaxyDriverShutdownTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests/Runtime/GalaxyDriverShutdownTests.cs
@@ -68,10 +68,22 @@ public sealed class GalaxyDriverShutdownTests
         public async IAsyncEnumerable<MxEvent> StreamEventsAsync([EnumeratorCancellation] CancellationToken cancellationToken)
         {
             Interlocked.Increment(ref StreamsOpened);
-            using var _ = cancellationToken.Register(() => StreamCancelled.TrySetResult());
-            await foreach (var ev in _events.Reader.ReadAllAsync(cancellationToken).ConfigureAwait(false))
+            // Signal from the iterator's own exit, not from a token registration: a registration made
+            // here is disposed by the `using` when the cancelled ReadAllAsync resumes the body on a
+            // pool thread — which can happen while Cancel() on the pump's thread is still walking its
+            // callback list, unregistering ours before it runs (CTS runs callbacks newest-first, and
+            // ReadAllAsync's is newer). Observed ~1% under parallel load as a 10 s timeout. A finally
+            // also proves the stronger fact: the stream actually ended because it was cancelled.
+            try
             {
-                yield return ev;
+                await foreach (var ev in _events.Reader.ReadAllAsync(cancellationToken).ConfigureAwait(false))
+                {
+                    yield return ev;
+                }
+            }
+            finally
+            {
+                if (cancellationToken.IsCancellationRequested) StreamCancelled.TrySetResult();
             }
         }