diff --git a/changelog.d/13501.misc b/changelog.d/13501.misc
new file mode 100644
index 000000000..002b91960
--- /dev/null
+++ b/changelog.d/13501.misc
@@ -0,0 +1 @@
+Revert 'Remove the unspecced `room_id` field in the `/hierarchy` response. (#13365)' to give more time for clients to update.
diff --git a/synapse/handlers/room_summary.py b/synapse/handlers/room_summary.py
index ebd445adc..732b0310b 100644
--- a/synapse/handlers/room_summary.py
+++ b/synapse/handlers/room_summary.py
@@ -453,6 +453,7 @@ class RoomSummaryHandler:
                 "type": e.type,
                 "state_key": e.state_key,
                 "content": e.content,
+                "room_id": e.room_id,
                 "sender": e.sender,
                 "origin_server_ts": e.origin_server_ts,
             }