1 files changed, 5 insertions, 0 deletions
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index a9dc4a4e4e..5280d88a50 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -1664,6 +1664,11 @@ class FederationHandler(BaseHandler):
                 create_event = e
                 break
 
+        if create_event is None:
+            # If the state doesn't have a create event then the room is
+            # invalid, and it would fail auth checks anyway.
+            raise SynapseError(400, "No create event in state")
+
         room_version = create_event.content.get("room_version", RoomVersions.V1)
 
         missing_auth_events = set()