diff --git a/synapse/storage/schema/delta/35/device_outbox_again.py b/synapse/storage/schema/delta/35/device_outbox_again.py
index 46da12a93c..d6d2260393 100644
--- a/synapse/storage/schema/delta/35/device_outbox_again.py
+++ b/synapse/storage/schema/delta/35/device_outbox_again.py
@@ -28,3 +28,7 @@ def run_create(cur, database_engine, *args, **kwargs):
         )
     except:
         pass
+
+
+def run_upgrade(cur, database_engine, *args, **kwargs):
+    pass