diff --git a/hardware/arduino/sam/cores/arduino/Printable.h b/hardware/arduino/sam/cores/arduino/Printable.h
index 54f7d717c..2a1b2e9f2 100644
--- a/hardware/arduino/sam/cores/arduino/Printable.h
+++ b/hardware/arduino/sam/cores/arduino/Printable.h
@@ -20,6 +20,8 @@
 #ifndef Printable_h
 #define Printable_h
 
+#include <stdlib.h>
+
 class Print;
 
 /** The Printable class provides a way for new classes to allow themselves to be printed.