diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 074363e80d..53ccaa0991 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -222,8 +222,7 @@ class MessageHandler(BaseHandler):
         if stamp_event:
             event.content["hsob_ts"] = int(self.clock.time_msec())
 
-        snapshot = yield self.store.snapshot_room(event.room_id, user_id)
-
+        snapshot = yield self.store.snapshot_room(event.room_id, event.user_id)
 
         yield self.auth.check(event, snapshot, raises=True)
 
@@ -577,8 +576,8 @@ class RoomMemberHandler(BaseHandler):
             content=content,
         )
 
-        snapshot = yield store.snapshot_room(
-            room_id, joinee, RoomMemberEvent.TYPE, event.target_user_id
+        snapshot = yield self.store.snapshot_room(
+            room_id, joinee, RoomMemberEvent.TYPE, joinee
         )
 
         yield self._do_join(new_event, snapshot, room_host=host, do_auth=True)
diff --git a/synapse/storage/__init__.py b/synapse/storage/__init__.py
index 30dc8a50cf..63afca9ad7 100644
--- a/synapse/storage/__init__.py
+++ b/synapse/storage/__init__.py
@@ -69,7 +69,7 @@ class DataStore(RoomMemberStore, RoomStore,
             stream_ordering = self.min_token
 
         latest = yield self._db_pool.runInteraction(
-            _persist_event_txn, event, backfilled, stream_ordering
+            self._persist_event_txn, event, backfilled, stream_ordering
         )
         defer.returnValue(latest)
 
@@ -128,7 +128,7 @@ class DataStore(RoomMemberStore, RoomStore,
         except:
             logger.exception(
                 "Failed to persist, probably duplicate: %s",
-                event_id
+                event.event_id
             )
             return
 
@@ -146,7 +146,7 @@ class DataStore(RoomMemberStore, RoomStore,
             self._simple_insert_txn(txn, "state_events", vals)
 
             self._simple_insert_txn(
-                txn
+                txn,
                 "current_state_events",
                 {
                     "event_id": event.event_id,