diff --git a/tests/backend/mongodb/test_changefeed.py b/tests/backend/mongodb/test_changefeed.py
index 67b54cd8..00dcaca5 100644
--- a/tests/backend/mongodb/test_changefeed.py
+++ b/tests/backend/mongodb/test_changefeed.py
@@ -19,7 +19,7 @@ def mock_changefeed_data():
         {
             'op': 'u',
             'o': {'msg': 'seems like we have an update here'},
-            'o2': 'some-id'
+            'o2': {'_id': 'some-id'}
         },
     ]