diff --git a/changelog.d/15678.misc b/changelog.d/15678.misc
new file mode 100644
index 000000000..92eae4995
--- /dev/null
+++ b/changelog.d/15678.misc
@@ -0,0 +1 @@
+Implement "option 2" for [MSC3820](https://github.com/matrix-org/matrix-spec-proposals/pull/3820): Room version 11.
\ No newline at end of file
diff --git a/synapse/api/room_versions.py b/synapse/api/room_versions.py
index 035a14171..c5c71e242 100644
--- a/synapse/api/room_versions.py
+++ b/synapse/api/room_versions.py
@@ -528,6 +528,7 @@ KNOWN_ROOM_VERSIONS: Dict[str, RoomVersion] = {
         RoomVersions.V10,
         RoomVersions.MSC2716v4,
         RoomVersions.MSC3989,
+        RoomVersions.MSC3820opt2,
     )
 }