diff --git a/changelog.d/12398.misc b/changelog.d/12398.misc
new file mode 100644
index 000000000000..f94054bdaaf5
--- /dev/null
+++ b/changelog.d/12398.misc
@@ -0,0 +1 @@
+Remove support for the unstable identifiers specified in [MSC3288](https://github.com/matrix-org/matrix-doc/pull/3288).
diff --git a/synapse/handlers/identity.py b/synapse/handlers/identity.py
index 57c9fdfe629a..c183e9c46523 100644
--- a/synapse/handlers/identity.py
+++ b/synapse/handlers/identity.py
@@ -858,8 +858,6 @@ async def ask_id_server_for_third_party_invite(
 
         if room_type is not None:
             invite_config["room_type"] = room_type
-            # TODO The unstable field is deprecated and should be removed in the future.
-            invite_config["org.matrix.msc3288.room_type"] = room_type
 
         # If a custom web client location is available, include it in the request.
         if self._web_client_location: