diff --git a/schemas/2022-08-01-preview/Microsoft.Resources.json b/schemas/2022-08-01-preview/Microsoft.Resources.json
index 47e6b093fb..7deeb7f9df 100644
--- a/schemas/2022-08-01-preview/Microsoft.Resources.json
+++ b/schemas/2022-08-01-preview/Microsoft.Resources.json
@@ -328,6 +328,9 @@
           "description": "denySettings Mode."
         }
       },
+      "required": [
+        "mode"
+      ],
       "description": "Defines how resources deployed by the deployment stack are locked."
     },
     "DeploymentStackProperties": {