diff --git a/synapse/handlers/sliding_sync/room_lists.py b/synapse/handlers/sliding_sync/room_lists.py
index 4238421a38..7e9e09c6ca 100644
--- a/synapse/handlers/sliding_sync/room_lists.py
+++ b/synapse/handlers/sliding_sync/room_lists.py
@@ -799,6 +799,9 @@ class SlidingSyncRoomLists:
                         )
                     )
                     rooms_should_send.update(rooms_that_have_updates)
+
+                    # Any rooms with receipts should be considered for sending as their
+                    # notification counts may have changed.
                     rooms_should_send.update(receipts.keys())
 
                     relevant_rooms_to_send_map = {