diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index ed182c8d1..6dc46fa50 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -189,6 +189,14 @@ class EventsStore(SQLBaseStore):
             self._background_reindex_fields_sender,
         )
 
+        self.register_background_index_update(
+            "event_contains_url_index",
+            index_name="event_contains_url_index",
+            table="events",
+            columns=["room_id", "topological_ordering", "stream_ordering"],
+            where_clause="contains_url = true AND outlier = false",
+        )
+
         self._event_persist_queue = _EventPeristenceQueue()
 
     def persist_events(self, events_and_contexts, backfilled=False):
diff --git a/synapse/storage/schema/delta/35/contains_url.sql b/synapse/storage/schema/delta/35/contains_url.sql
new file mode 100644
index 000000000..6cd123027
--- /dev/null
+++ b/synapse/storage/schema/delta/35/contains_url.sql
@@ -0,0 +1,17 @@
+/* Copyright 2016 OpenMarket Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+ INSERT into background_updates (update_name, progress_json)
+     VALUES ('event_contains_url_index', '{}');