diff --git a/synapse/storage/event_federation.py b/synapse/storage/event_federation.py
index 989ad340b036a1ec517c50c5c10759d012c7425a..c1cabbaa60ed32b7e47af6d1b86b11faba049aa1 100644
--- a/synapse/storage/event_federation.py
+++ b/synapse/storage/event_federation.py
@@ -303,6 +303,15 @@ class EventFederationStore(SQLBaseStore):
             ],
         )
 
+        self._update_extremeties(txn, events)
+
+    def _update_extremeties(self, txn, events):
+        """Updates the event_*_extremities tables based on the new/updated
+        events being persisted.
+
+        This is called for new events *and* for events that were outliers, but
+        are are now being persisted as non-outliers.
+        """
         events_by_room = {}
         for ev in events:
             events_by_room.setdefault(ev.room_id, []).append(ev)
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index fba837f461f5fc388cf1ddfabd14c1075fa2cf91..0a477e3122c61731f778bf52d972c70cd037a12d 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -281,6 +281,8 @@ class EventsStore(SQLBaseStore):
                     (False, event.event_id,)
                 )
 
+                self._update_extremeties(txn, [event])
+
         events_and_contexts = filter(
             lambda ec: ec[0] not in to_remove,
             events_and_contexts