diff --git a/tests/rest/client/test_rooms.py b/tests/rest/client/test_rooms.py
index b384c7c489..0dc9562a80 100644
--- a/tests/rest/client/test_rooms.py
+++ b/tests/rest/client/test_rooms.py
@@ -1211,7 +1211,7 @@ class RoomMemberStateTestCase(RoomBase):
         )
 
         # Even no-op membership changes should be rejected
-        content = '{"membership":"%s"}' % Membership.JOIN
+        content = '{"membership":"%s", "key_to_cause_new_event":1}' % Membership.JOIN
         channel = self.make_request("PUT", path, content.encode("ascii"))
         self.assertEqual(HTTPStatus.FORBIDDEN, channel.code, msg=channel.result["body"])