diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index fcc109176..976d98387 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -531,7 +531,7 @@ class RoomEventServlet(ClientV1RestServlet):
 
     @defer.inlineCallbacks
     def on_GET(self, request, room_id, event_id):
-        requester = yield self.auth.get_user_by_req(request)
+        requester = yield self.auth.get_user_by_req(request, allow_guest=True)
         event = yield self.event_handler.get_event(requester.user, room_id, event_id)
 
         time_now = self.clock.time_msec()