diff --git a/synapse/handlers/room_list.py b/synapse/handlers/room_list.py
index 1e883b23f6..667223df0c 100644
--- a/synapse/handlers/room_list.py
+++ b/synapse/handlers/room_list.py
@@ -62,7 +62,7 @@ class RoomListHandler(BaseHandler):
                 appservice and network id to use an appservice specific one.
                 Setting to None returns all public rooms across all lists.
         """
-        if search_filter or network_tuple is not (None, None):
+        if search_filter or (network_tuple and network_tuple.appservice_id is not None):
             # We explicitly don't bother caching searches or requests for
             # appservice specific lists.
             return self._get_public_room_list(
@@ -73,7 +73,9 @@ class RoomListHandler(BaseHandler):
         if not result:
             result = self.response_cache.set(
                 (limit, since_token),
-                self._get_public_room_list(limit, since_token)
+                self._get_public_room_list(
+                    limit, since_token, network_tuple=network_tuple
+                )
             )
         return result