diff --git a/specification/resources/resource-manager/Microsoft.Resources/preview/2022-08-01-preview/deploymentStacks.json b/specification/resources/resource-manager/Microsoft.Resources/preview/2022-08-01-preview/deploymentStacks.json
index 6d00e7f34d35..36f4c1865819 100644
--- a/specification/resources/resource-manager/Microsoft.Resources/preview/2022-08-01-preview/deploymentStacks.json
+++ b/specification/resources/resource-manager/Microsoft.Resources/preview/2022-08-01-preview/deploymentStacks.json
@@ -1050,6 +1050,9 @@
     "DenySettings": {
       "description": "Defines how resources deployed by the deployment stack are locked.",
       "type": "object",
+      "required": [
+        "mode"
+      ],
       "properties": {
         "mode": {
           "type": "string",