diff --git a/FreeRTOS-Plus/Demo/corePKCS11_MQTT_Mutual_Auth_Windows_Simulator/demo_config.h b/FreeRTOS-Plus/Demo/corePKCS11_MQTT_Mutual_Auth_Windows_Simulator/demo_config.h
index b0969e6aa9..3f0ba4582b 100644
--- a/FreeRTOS-Plus/Demo/corePKCS11_MQTT_Mutual_Auth_Windows_Simulator/demo_config.h
+++ b/FreeRTOS-Plus/Demo/corePKCS11_MQTT_Mutual_Auth_Windows_Simulator/demo_config.h
@@ -60,6 +60,11 @@
  * must be unique; so edit as required to ensure that no two clients connecting to
  * the same broker use the same client identifier.
  *
+ *!!! Please note a #defined constant is used for convenience of demonstration
+ *!!! only.  Production devices can use something unique to the device that can
+ *!!! be read by software, such as a production serial number, instead of a
+ *!!! hard coded constant.
+ *
  * #define democonfigCLIENT_IDENTIFIER    "insert here."
  */