diff --git a/iot/mqtt_example/cloudiot_mqtt_example_nodejs.js b/iot/mqtt_example/cloudiot_mqtt_example_nodejs.js
index 901adae3d4..bd6763fd1d 100644
--- a/iot/mqtt_example/cloudiot_mqtt_example_nodejs.js
+++ b/iot/mqtt_example/cloudiot_mqtt_example_nodejs.js
@@ -202,6 +202,7 @@ let connectionArgs = {
 let iatTime = parseInt(Date.now() / 1000);
 let client = mqtt.connect(connectionArgs);
 
+// Subscribe to the /devices/{device-id}/config topic to receive config updates.
 client.subscribe(`/devices/${argv.deviceId}/config`);
 
 // The MQTT topic that this device will publish data to. The MQTT