diff --git a/openapi.yaml b/openapi.yaml
index ce3e988c3..c0c3049fd 100644
--- a/openapi.yaml
+++ b/openapi.yaml
@@ -1803,6 +1803,7 @@ components:
           type: string
           description: in IS0 8601 format. eg. `1963-11-22T18:30:00Z`
           format: date-time
+          nullable: true
         deviceLimit:
           type: integer
         userLimit: