diff --git a/specification/synapse/data-plane/Microsoft.Synapse/preview/2019-06-01-preview/artifacts.json b/specification/synapse/data-plane/Microsoft.Synapse/preview/2019-06-01-preview/artifacts.json
index ac09b634bc57..2a2571199bd6 100644
--- a/specification/synapse/data-plane/Microsoft.Synapse/preview/2019-06-01-preview/artifacts.json
+++ b/specification/synapse/data-plane/Microsoft.Synapse/preview/2019-06-01-preview/artifacts.json
@@ -4107,7 +4107,8 @@
           "description": "The end time of a pipeline run in ISO8601 format.",
           "type": "string",
           "format": "date-time",
-          "readOnly": true
+          "readOnly": true,
+          "x-nullable": true
         },
         "durationInMs": {
           "description": "The duration of a pipeline run.",