diff --git a/mbed.h b/mbed.h
index 1e56e636401..b1ecae4769c 100644
--- a/mbed.h
+++ b/mbed.h
@@ -16,6 +16,8 @@
 #ifndef MBED_H
 #define MBED_H
 
+#warning test
+
 #if MBED_CONF_RTOS_PRESENT
 #include "rtos/rtos.h"
 #endif