diff --git a/cfg.lex b/cfg.lex
index c9e57b7a4b0..b08d4fdc65f 100644
--- a/cfg.lex
+++ b/cfg.lex
@@ -66,6 +66,7 @@
 	#include "mem/mem.h"
 	#include <string.h>
 	#include <stdlib.h>
+	#include <unistd.h>
 	#include "ip_addr.h"