diff --git a/synapse/handlers/user_directory.py b/synapse/handlers/user_directory.py
index c7a3acafc..9f0d3499e 100644
--- a/synapse/handlers/user_directory.py
+++ b/synapse/handlers/user_directory.py
@@ -187,9 +187,9 @@ class UserDirectoyHandler(object):
         if is_public:
             yield self.store.add_users_to_public_room(
                 room_id,
-                user_ids=unhandled_users - self.initially_handled_users_in_public
+                user_ids=user_ids - self.initially_handled_users_in_public
             )
-            self.initially_handled_users_in_public != unhandled_users
+            self.initially_handled_users_in_public != user_ids
 
         # We now go and figure out the new users who share rooms with user entries
         # We sleep aggressively here as otherwise it can starve resources.