diff -Naur mailx-support-20060102.orig/open_with_exlock.c mailx-support-20060102/open_with_exlock.c
--- mailx-support-20060102.orig/open_with_exlock.c	2003-06-09 19:01:08.000000000 +0000
+++ mailx-support-20060102/open_with_exlock.c	2014-04-01 12:17:31.830213927 +0000
@@ -1,4 +1,5 @@
 #include <fcntl.h>
+#include <sys/file.h>
 
 int open_with_exlock(const char *path, int flags, mode_t mode)
 {