diff --git a/synapse/app/event_creator.py b/synapse/app/event_creator.py
index a2bdaf2a2c..a34c89fa99 100644
--- a/synapse/app/event_creator.py
+++ b/synapse/app/event_creator.py
@@ -68,6 +68,8 @@ logger = logging.getLogger("synapse.app.event_creator")
 
 
 class EventCreatorSlavedStore(
+    # FIXME(#3714): We need to add UserDirectoryStore as we write directly
+    # rather than going via the correct worker.
     UserDirectoryStore,
     DirectoryStore,
     SlavedTransactionStore,
diff --git a/synapse/handlers/user_directory.py b/synapse/handlers/user_directory.py
index 37dda64587..d8413d6aa7 100644
--- a/synapse/handlers/user_directory.py
+++ b/synapse/handlers/user_directory.py
@@ -119,6 +119,8 @@ class UserDirectoryHandler(object):
         """Called to update index of our local user profiles when they change
         irrespective of any rooms the user may be in.
         """
+        # FIXME(#3714): We should probably do this in the same worker as all
+        # the other changes.
         yield self.store.update_profile_in_user_dir(
             user_id, profile.display_name, profile.avatar_url, None,
         )
@@ -127,6 +129,8 @@ class UserDirectoryHandler(object):
     def handle_user_deactivated(self, user_id):
         """Called when a user ID is deactivated
         """
+        # FIXME(#3714): We should probably do this in the same worker as all
+        # the other changes.
         yield self.store.remove_from_user_dir(user_id)
         yield self.store.remove_from_user_in_public_room(user_id)