diff --git a/src/boards/rt-01.c b/src/boards/rt-01.c
index c724b74..ee3e5e5 100644
--- a/src/boards/rt-01.c
+++ b/src/boards/rt-01.c
@@ -24,6 +24,7 @@
  * 
  */
 
+#include <stdlib.h>
 #include "mapinc.h"
 
 static DECLFR(UNLRT01Read) {