diff --git a/api/client-server/definitions/sync_filter.yaml b/api/client-server/definitions/sync_filter.yaml
index fc154f3a..1691ca31 100644
--- a/api/client-server/definitions/sync_filter.yaml
+++ b/api/client-server/definitions/sync_filter.yaml
@@ -26,6 +26,21 @@ properties:
     description: The user account data that isn't associated with rooms to include.
   room:
     properties:
+      not_rooms:
+        description: A list of room IDs to exclude. If this list is absent then no rooms
+          are excluded. A matching room will be excluded even if it is listed in the 'rooms'
+          filter. This filter is applied before the filters in ``ephemeral``, 
+          ``state``, ``timeline`` or ``account_data``
+        items:
+          type: string
+        type: array
+      rooms:
+        description: A list of room IDs to include. If this list is absent then all rooms
+          are included. This filter is applied before the filters in ``ephemeral``,
+          ``state``, ``timeline`` or ``account_data``
+        items:
+          type: string
+        type: array
       ephemeral:
         allOf:
         - $ref: room_event_filter.yaml