diff -urN flow-tools-0.68/src/flow-header.c flow-tools-0.68.s/src/flow-header.c
--- flow-tools-0.68/src/flow-header.c	2003-04-02 22:03:02.000000000 +0400
+++ flow-tools-0.68.s/src/flow-header.c	2007-03-24 23:35:30.000000000 +0300
@@ -32,6 +32,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 void usage(void);