diff --git a/changelog.d/12156.misc b/changelog.d/12156.misc
new file mode 100644
index 000000000..4818d988d
--- /dev/null
+++ b/changelog.d/12156.misc
@@ -0,0 +1 @@
+Fix some type annotations.
diff --git a/synapse/state/__init__.py b/synapse/state/__init__.py
index 6babd5963..21888cc8c 100644
--- a/synapse/state/__init__.py
+++ b/synapse/state/__init__.py
@@ -194,7 +194,7 @@ class StateHandler:
         }
 
     async def get_current_state_ids(
-        self, room_id: str, latest_event_ids: Optional[Iterable[str]] = None
+        self, room_id: str, latest_event_ids: Optional[Collection[str]] = None
     ) -> StateMap[str]:
         """Get the current state, or the state at a set of events, for a room
 
@@ -243,7 +243,7 @@ class StateHandler:
         return await self.get_hosts_in_room_at_events(room_id, event_ids)
 
     async def get_hosts_in_room_at_events(
-        self, room_id: str, event_ids: Iterable[str]
+        self, room_id: str, event_ids: Collection[str]
     ) -> Set[str]:
         """Get the hosts that were in a room at the given event ids
 
@@ -404,7 +404,7 @@ class StateHandler:
 
     @measure_func()
     async def resolve_state_groups_for_events(
-        self, room_id: str, event_ids: Iterable[str]
+        self, room_id: str, event_ids: Collection[str]
     ) -> _StateCacheEntry:
         """Given a list of event_ids this method fetches the state at each
         event, resolves conflicts between them and returns them.
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index e79ecf64a..86f1a5373 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -561,7 +561,7 @@ class StateGroupStorage:
         return state_group_delta.prev_group, state_group_delta.delta_ids
 
     async def get_state_groups_ids(
-        self, _room_id: str, event_ids: Iterable[str]
+        self, _room_id: str, event_ids: Collection[str]
     ) -> Dict[int, MutableStateMap[str]]:
         """Get the event IDs of all the state for the state groups for the given events
 
@@ -596,7 +596,7 @@ class StateGroupStorage:
         return group_to_state[state_group]
 
     async def get_state_groups(
-        self, room_id: str, event_ids: Iterable[str]
+        self, room_id: str, event_ids: Collection[str]
     ) -> Dict[int, List[EventBase]]:
         """Get the state groups for the given list of event_ids
 
@@ -648,7 +648,7 @@ class StateGroupStorage:
         return self.stores.state._get_state_groups_from_groups(groups, state_filter)
 
     async def get_state_for_events(
-        self, event_ids: Iterable[str], state_filter: Optional[StateFilter] = None
+        self, event_ids: Collection[str], state_filter: Optional[StateFilter] = None
     ) -> Dict[str, StateMap[EventBase]]:
         """Given a list of event_ids and type tuples, return a list of state
         dicts for each event.
@@ -684,7 +684,7 @@ class StateGroupStorage:
         return {event: event_to_state[event] for event in event_ids}
 
     async def get_state_ids_for_events(
-        self, event_ids: Iterable[str], state_filter: Optional[StateFilter] = None
+        self, event_ids: Collection[str], state_filter: Optional[StateFilter] = None
     ) -> Dict[str, StateMap[str]]:
         """
         Get the state dicts corresponding to a list of events, containing the event_ids