diff --git a/synapse/storage/databases/main/user_directory.py b/synapse/storage/databases/main/user_directory.py
index 1c73e51c21..33eee96a47 100644
--- a/synapse/storage/databases/main/user_directory.py
+++ b/synapse/storage/databases/main/user_directory.py
@@ -695,7 +695,7 @@ class UserDirectoryStore(UserDirectoryBackgroundUpdateStore):
             user_id,
             other_user_id,
             user_id,
-            other_user_id
+            other_user_id,
         )
         return list({row[0] for row in rows})