diff --git a/specification/machinelearningservices/resource-manager/Microsoft.MachineLearningServices/stable/2021-10-01/machineLearningServices.json b/specification/machinelearningservices/resource-manager/Microsoft.MachineLearningServices/stable/2021-10-01/machineLearningServices.json
index 2a80be932300..906d874657cf 100644
--- a/specification/machinelearningservices/resource-manager/Microsoft.MachineLearningServices/stable/2021-10-01/machineLearningServices.json
+++ b/specification/machinelearningservices/resource-manager/Microsoft.MachineLearningServices/stable/2021-10-01/machineLearningServices.json
@@ -3321,7 +3321,8 @@
         "subnet": {
           "title": "Subnet.",
           "description": "Virtual network subnet resource ID the compute nodes belong to.",
-          "$ref": "#/definitions/ResourceId"
+          "$ref": "#/definitions/ResourceId",
+          "x-nullable": true
         },
         "remoteLoginPortPublicAccess": {
           "type": "string",