1 files changed, 2 insertions, 2 deletions
diff --git a/synapse/storage/databases/state/store.py b/synapse/storage/databases/state/store.py
index 989f0cbc9d..0e31cc811a 100644
--- a/synapse/storage/databases/state/store.py
+++ b/synapse/storage/databases/state/store.py
@@ -24,7 +24,7 @@ from synapse.storage.databases.state.bg_updates import StateBackgroundUpdateStor
 from synapse.storage.state import StateFilter
 from synapse.storage.types import Cursor
 from synapse.storage.util.sequence import build_sequence_generator
-from synapse.types import StateMap
+from synapse.types import MutableStateMap, StateMap
 from synapse.util.caches.descriptors import cached
 from synapse.util.caches.dictionary_cache import DictionaryCache
 
@@ -208,7 +208,7 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
 
     async def _get_state_for_groups(
         self, groups: Iterable[int], state_filter: StateFilter = StateFilter.all()
-    ) -> Dict[int, StateMap[str]]:
+    ) -> Dict[int, MutableStateMap[str]]:
         """Gets the state at each of a list of state groups, optionally
         filtering by type/state_key