diff --git a/specification/compute/resource-manager/Microsoft.Compute/stable/2019-07-01/compute.json b/specification/compute/resource-manager/Microsoft.Compute/stable/2019-07-01/compute.json
index 275b9ee2138c..f4cbbdf6216f 100644
--- a/specification/compute/resource-manager/Microsoft.Compute/stable/2019-07-01/compute.json
+++ b/specification/compute/resource-manager/Microsoft.Compute/stable/2019-07-01/compute.json
@@ -3589,6 +3589,66 @@
         },
         "x-ms-long-running-operation": true
       },
+      "patch": {
+        "tags": [
+          "VirtualMachineScaleSetExtensions"
+        ],
+        "operationId": "VirtualMachineScaleSetExtensions_Update",
+        "description": "The operation to update an extension.",
+        "parameters": [
+          {
+            "name": "resourceGroupName",
+            "in": "path",
+            "required": true,
+            "type": "string",
+            "description": "The name of the resource group."
+          },
+          {
+            "name": "vmScaleSetName",
+            "in": "path",
+            "required": true,
+            "type": "string",
+            "description": "The name of the VM scale set where the extension should be updated."
+          },
+          {
+            "name": "vmssExtensionName",
+            "in": "path",
+            "required": true,
+            "type": "string",
+            "description": "The name of the VM scale set extension."
+          },
+          {
+            "name": "extensionParameters",
+            "in": "body",
+            "required": true,
+            "schema": {
+              "$ref": "#/definitions/VirtualMachineScaleSetExtensionUpdate"
+            },
+            "description": "Parameters supplied to the Update VM scale set Extension operation."
+          },
+          {
+            "$ref": "#/parameters/ApiVersionParameter"
+          },
+          {
+            "$ref": "#/parameters/SubscriptionIdParameter"
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "OK",
+            "schema": {
+              "$ref": "#/definitions/VirtualMachineScaleSetExtension"
+            }
+          },
+          "201": {
+            "description": "Created",
+            "schema": {
+              "$ref": "#/definitions/VirtualMachineScaleSetExtension"
+            }
+          }
+        },
+        "x-ms-long-running-operation": true
+      },
       "delete": {
         "tags": [
           "VirtualMachineScaleSetExtensions"
@@ -9007,6 +9067,35 @@
           "type": "string",
           "description": "The name of the extension."
         },
+        "type": {
+          "readOnly": true,
+          "type": "string",
+          "description": "Resource type"
+        },
+        "properties": {
+          "x-ms-client-flatten": true,
+          "$ref": "#/definitions/VirtualMachineScaleSetExtensionProperties"
+        }
+      },
+      "allOf": [
+        {
+          "$ref": "#/definitions/SubResourceReadOnly"
+        }
+      ],
+      "description": "Describes a Virtual Machine Scale Set Extension."
+    },
+    "VirtualMachineScaleSetExtensionUpdate": {
+      "properties": {
+        "name": {
+          "readOnly": true,
+          "type": "string",
+          "description": "The name of the extension."
+        },
+        "type": {
+          "readOnly": true,
+          "type": "string",
+          "description": "Resource type"
+        },
         "properties": {
           "x-ms-client-flatten": true,
           "$ref": "#/definitions/VirtualMachineScaleSetExtensionProperties"