diff --git a/changelog.d/6153.misc b/changelog.d/6153.misc
new file mode 100644
index 0000000000..dfee73c28f
--- /dev/null
+++ b/changelog.d/6153.misc
@@ -0,0 +1 @@
+Improve performance of the public room list directory.
diff --git a/synapse/storage/room.py b/synapse/storage/room.py
index 9b7e31583c..615c0d3f65 100644
--- a/synapse/storage/room.py
+++ b/synapse/storage/room.py
@@ -174,6 +174,9 @@ class RoomWorkerStore(SQLBaseStore):
 
             query_args += [last_joined_members, last_joined_members, last_room_id]
 
+        if ignore_non_federatable:
+            where_clauses.append("is_federatable")
+
         if search_filter and search_filter.get("generic_search_term", None):
             search_term = "%" + search_filter["generic_search_term"] + "%"