diff --git a/ftdi-gpio.c b/ftdi-gpio.c
index b49e267..0066cc2 100644
--- a/ftdi-gpio.c
+++ b/ftdi-gpio.c
@@ -38,6 +38,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 #include "cdba-server.h"
 #include "ftdi-gpio.h"