diff --git a/api/client-server/definitions/room_event_filter.yaml b/api/client-server/definitions/room_event_filter.yaml
index 9817db0c..c36b3768 100644
--- a/api/client-server/definitions/room_event_filter.yaml
+++ b/api/client-server/definitions/room_event_filter.yaml
@@ -31,5 +31,5 @@ allOf:
       type: array
     contains_url:
       type: boolean
-    description: If ``true``, includes only events with a url key in their content. If
-      ``false``, excludes those events.
+      description: If ``true``, includes only events with a ``url`` key in their content. If
+        ``false``, excludes those events. Defaults to ``false``.