1 files changed, 3 insertions, 1 deletions
diff --git a/synapse/storage/databases/main/stream.py b/synapse/storage/databases/main/stream.py
index 959f13de47..9a3b6f4acf 100644
--- a/synapse/storage/databases/main/stream.py
+++ b/synapse/storage/databases/main/stream.py
@@ -39,6 +39,8 @@ import logging
 from collections import namedtuple
 from typing import TYPE_CHECKING, Collection, Dict, List, Optional, Set, Tuple
 
+from frozendict import frozendict
+
 from twisted.internet import defer
 
 from synapse.api.filtering import Filter
@@ -379,7 +381,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore, metaclass=abc.ABCMeta):
                 if p > min_pos
             }
 
-        return RoomStreamToken(None, min_pos, positions)
+        return RoomStreamToken(None, min_pos, frozendict(positions))
 
     async def get_room_events_stream_for_rooms(
         self,