diff --git a/wiring.c b/wiring.c
index 6c71e6e9..1b7236e4 100644
--- a/wiring.c
+++ b/wiring.c
@@ -43,6 +43,7 @@
 
 #include <stdio.h>
 #include <string.h>
+#include <stdlib.h>
 #include <unistd.h>
 
 #include "avrdude.h"