diff --git a/specification/appconfiguration/resource-manager/Microsoft.AppConfiguration/preview/2021-03-01-preview/appconfiguration.json b/specification/appconfiguration/resource-manager/Microsoft.AppConfiguration/preview/2021-03-01-preview/appconfiguration.json
index 8a3a3807eee3..0607f2b84c9f 100644
--- a/specification/appconfiguration/resource-manager/Microsoft.AppConfiguration/preview/2021-03-01-preview/appconfiguration.json
+++ b/specification/appconfiguration/resource-manager/Microsoft.AppConfiguration/preview/2021-03-01-preview/appconfiguration.json
@@ -1575,6 +1575,10 @@
           "items": {
             "$ref": "#/definitions/MetricDimension"
           }
+        },
+        "fillGapWithZero": {
+          "description": "Optional. If set to true, then zero will be returned for time duration where no metric is emitted/published.",
+          "type": "boolean"
         }
       }
     },