diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index c659004e8..58b73af7d 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -60,12 +60,12 @@ class LoggingTransaction(object):
         object.__setattr__(self, "database_engine", database_engine)
         object.__setattr__(self, "after_callbacks", after_callbacks)
 
-    def call_after(self, callback, *args):
+    def call_after(self, callback, *args, **kwargs):
         """Call the given callback on the main twisted thread after the
         transaction has finished. Used to invalidate the caches on the
         correct thread.
         """
-        self.after_callbacks.append((callback, args))
+        self.after_callbacks.append((callback, args, kwargs))
 
     def __getattr__(self, name):
         return getattr(self.txn, name)
@@ -319,8 +319,8 @@ class SQLBaseStore(object):
                     inner_func, *args, **kwargs
                 )
         finally:
-            for after_callback, after_args in after_callbacks:
-                after_callback(*after_args)
+            for after_callback, after_args, after_kwargs in after_callbacks:
+                after_callback(*after_args, **after_kwargs)
         defer.returnValue(result)
 
     @defer.inlineCallbacks
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index ea6879c61..c4aeb4880 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -399,6 +399,11 @@ class EventsStore(SQLBaseStore):
 
                     event_counter.inc(event.type, origin_type, origin_entity)
 
+                for room_id, (_, _, new_state) in current_state_for_room.iteritems():
+                    self.get_current_state_ids.prefill(
+                        (room_id, ), new_state
+                    )
+
     @defer.inlineCallbacks
     def _calculate_new_extremeties(self, room_id, event_contexts, latest_event_ids):
         """Calculates the new forward extremeties for a room given events to
@@ -447,10 +452,10 @@ class EventsStore(SQLBaseStore):
         Assumes that we are only persisting events for one room at a time.
 
         Returns:
-            2-tuple (to_delete, to_insert) where both are state dicts, i.e.
-            (type, state_key) -> event_id. `to_delete` are the entries to
+            3-tuple (to_delete, to_insert, new_state) where both are state dicts,
+            i.e. (type, state_key) -> event_id. `to_delete` are the entries to
             first be deleted from current_state_events, `to_insert` are entries
-            to insert.
+            to insert. `new_state` is the full set of state.
             May return None if there are no changes to be applied.
         """
         # Now we need to work out the different state sets for
@@ -557,7 +562,7 @@ class EventsStore(SQLBaseStore):
             if ev_id in events_to_insert
         }
 
-        defer.returnValue((to_delete, to_insert))
+        defer.returnValue((to_delete, to_insert, current_state))
 
     @defer.inlineCallbacks
     def get_event(self, event_id, check_redacted=True,
@@ -710,7 +715,7 @@ class EventsStore(SQLBaseStore):
 
     def _update_current_state_txn(self, txn, state_delta_by_room):
         for room_id, current_state_tuple in state_delta_by_room.iteritems():
-                to_delete, to_insert = current_state_tuple
+                to_delete, to_insert, _ = current_state_tuple
                 txn.executemany(
                     "DELETE FROM current_state_events WHERE event_id = ?",
                     [(ev_id,) for ev_id in to_delete.itervalues()],
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index a16afa8df..85acf2ad1 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -227,6 +227,18 @@ class StateStore(SQLBaseStore):
                     ],
                 )
 
+            # Prefill the state group cache with this group.
+            # It's fine to use the sequence like this as the state group map
+            # is immutable. (If the map wasn't immutable then this prefill could
+            # race with another update)
+            txn.call_after(
+                self._state_group_cache.update,
+                self._state_group_cache.sequence,
+                key=context.state_group,
+                value=dict(context.current_state_ids),
+                full=True,
+            )
+
         self._simple_insert_many_txn(
             txn,
             table="event_to_state_groups",