diff --git a/STM32F4/cores/maple/wirish.h b/STM32F4/cores/maple/wirish.h
index 75d4aec..4aca74c 100644
--- a/STM32F4/cores/maple/wirish.h
+++ b/STM32F4/cores/maple/wirish.h
@@ -33,6 +33,7 @@
 #ifndef _WIRISH_H_
 #define _WIRISH_H_
 
+#include <stdlib.h>
 #include "libmaple.h"
 
 #include "wirish_types.h"