diff --git a/apps/emqx_connector/src/mqtt/emqx_connector_mqtt_schema.erl b/apps/emqx_connector/src/mqtt/emqx_connector_mqtt_schema.erl
index b06d00884..438f33b5d 100644
--- a/apps/emqx_connector/src/mqtt/emqx_connector_mqtt_schema.erl
+++ b/apps/emqx_connector/src/mqtt/emqx_connector_mqtt_schema.erl
@@ -224,7 +224,7 @@ fields("egress") ->
             sc(
                 binary(),
                 #{
-                    required => true,
+                    default => <<"${payload}">>,
                     desc => ?DESC("payload")
                 }
             )}