diff --git a/changelogs/server_server/newsfragments/1398.feature b/changelogs/server_server/newsfragments/1398.feature
new file mode 100644
index 00000000..e5ca05a5
--- /dev/null
+++ b/changelogs/server_server/newsfragments/1398.feature
@@ -0,0 +1 @@
+Extend `/_matrix/federation/v2/send_join` to allow omitting membership events, per [MSC3706](https://github.com/matrix-org/matrix-doc/pull/3706).
\ No newline at end of file
diff --git a/data/api/server-server/joins-v2.yaml b/data/api/server-server/joins-v2.yaml
index 49467c21..1248c0c9 100644
--- a/data/api/server-server/joins-v2.yaml
+++ b/data/api/server-server/joins-v2.yaml
@@ -255,6 +255,7 @@ paths:
                   server's signature.
               servers_in_room:
                 type: array
+                x-addedInMatrixVersion: "1.6"
                 description: |-
                   **Required** if `members_omitted` is true.