1 files changed, 1 insertions, 1 deletions
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 9cff444779..16bac95331 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -65,7 +65,7 @@ class FederationHandler(BaseHandler):
             content.update({"membership": Membership.JOIN})
             new_event = self.event_factory.create_event(
                 etype=RoomMemberEvent.TYPE,
-                target_user_id=event.user_id,
+                state_key=event.user_id,
                 room_id=event.room_id,
                 user_id=event.user_id,
                 membership=Membership.JOIN,