diff -up dos2unix-3.1/dos2unix.c.missing-proto dos2unix-3.1/dos2unix.c
--- dos2unix-3.1/dos2unix.c.missing-proto	2008-04-14 17:11:58.000000000 +0100
+++ dos2unix-3.1/dos2unix.c	2008-04-14 17:12:42.000000000 +0100
@@ -75,6 +75,11 @@ static int macmode = 0;
 #include <string.h>
 #include <utime.h>
 #include <sys/stat.h>
+#if defined(__MSDOS__) || defined(__WIN32__) || defined(_WIN32)
+#  include <io.h>
+#else
+#  include <unistd.h>
+#endif
 #include "dos2unix.h"