1 files changed, 1 insertions, 1 deletions
diff --git a/tests/rest/client/test_retention.py b/tests/rest/client/test_retention.py
index d3e06bf6b3..534dc339f3 100644
--- a/tests/rest/client/test_retention.py
+++ b/tests/rest/client/test_retention.py
@@ -243,7 +243,7 @@ class RetentionTestCase(unittest.HomeserverTestCase):
         assert event is not None
 
         time_now = self.clock.time_msec()
-        serialized = self.serializer.serialize_event(event, time_now)
+        serialized = self.get_success(self.serializer.serialize_event(event, time_now))
 
         return serialized