diff --git a/arduino.c b/arduino.c
index 247f21a7..fd80567c 100644
--- a/arduino.c
+++ b/arduino.c
@@ -30,6 +30,7 @@
 
 #include <stdio.h>
 #include <string.h>
+#include <unistd.h>
 
 #include "avrdude.h"
 #include "pgm.h"