diff --git a/tractor/_clustering.py b/tractor/_clustering.py
index 8fabc00..d7255fd 100644
--- a/tractor/_clustering.py
+++ b/tractor/_clustering.py
@@ -51,3 +51,5 @@ async def open_actor_cluster(
 
         assert len(portals) == count
         yield portals
+
+        await an.cancel()