diff --git a/specification/ml/_types/Model.ts b/specification/ml/_types/Model.ts
index 89ad329dcc..06694f135b 100644
--- a/specification/ml/_types/Model.ts
+++ b/specification/ml/_types/Model.ts
@@ -52,7 +52,7 @@ export class ModelSnapshotUpgrade {
   /**
    * @availability stack
    */
-  node: DiscoveryNode
+  node?: DiscoveryNode
   assignment_explanation: string
 }