diff --git a/api/server-server/joins.yaml b/api/server-server/joins.yaml
index 472d63bf..759361b7 100644
--- a/api/server-server/joins.yaml
+++ b/api/server-server/joins.yaml
@@ -273,7 +273,7 @@ paths:
                       type: object
                       schema:
                         $ref: "definitions/pdu.yaml"
-                required: ["auth_chain", "state"]
+                required: ["auth_chain", "state", "origin"]
           examples:
             application/json: [
               200,