diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index 7f1fb3c394..19da2dcd02 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -208,7 +208,7 @@ class EventBase(metaclass=abc.ABCMeta):
 
         self.internal_metadata = EventInternalMetadata(internal_metadata_dict)
 
-        self._stitched_ordering = None
+        self._stitched_ordering: Optional[int] = None
 
     depth: DictProperty[int] = DictProperty("depth")
     content: DictProperty[JsonDict] = DictProperty("content")
diff --git a/synapse/storage/controllers/persist_events.py b/synapse/storage/controllers/persist_events.py
index 9b7d999deb..1ad124421a 100644
--- a/synapse/storage/controllers/persist_events.py
+++ b/synapse/storage/controllers/persist_events.py
@@ -1298,7 +1298,7 @@ async def assign_stitched_orders(
     gap_events = await store.db_pool.simple_select_many_batch(
         "event_backward_extremities",
         "event_id",
-        (ev.event_id for (ev, _) in events_and_contexts),
+        (ev.event_id for ev in remaining_batch),
         ["event_id", "before_gap_event_id"],
     )