diff --git a/synapse/api/filtering.py b/synapse/api/filtering.py
index 7158dd75e9..fd58961862 100644
--- a/synapse/api/filtering.py
+++ b/synapse/api/filtering.py
@@ -112,7 +112,10 @@ ROOM_EVENT_FILTER_SCHEMA = {
         },
         "contains_url": {
             "type": "boolean"
-        }
+        },
+        "lazy_load_members": {
+            "type": "boolean"
+        },
     }
 }