diff --git a/specification/datafactory/resource-manager/Microsoft.DataFactory/stable/2018-06-01/entityTypes/Trigger.json b/specification/datafactory/resource-manager/Microsoft.DataFactory/stable/2018-06-01/entityTypes/Trigger.json
index b9ff8cce6b89..fcc6219cd204 100644
--- a/specification/datafactory/resource-manager/Microsoft.DataFactory/stable/2018-06-01/entityTypes/Trigger.json
+++ b/specification/datafactory/resource-manager/Microsoft.DataFactory/stable/2018-06-01/entityTypes/Trigger.json
@@ -428,7 +428,8 @@
       "type": "string",
       "enum": [
         "Minute",
-        "Hour"
+        "Hour",
+        "Month"
       ],
       "x-ms-enum": {
         "name": "TumblingWindowFrequency",