diff --git a/tests/test_events.py b/tests/test_events.py
index 9900aaf2b..969d0492f 100644
--- a/tests/test_events.py
+++ b/tests/test_events.py
@@ -395,7 +395,7 @@ def cb(ev):
     try:
         em()
     except RuntimeError as err:
-        if str(err) != "Event source-stack mismatch.":
+        if "Event source-stack mismatch." not in str(err):
             raise
 
     em.disconnect()