diff -c sbin.orig/mount_union/mount_union.c sbin/mount_union/mount_union.c
*** sbin.orig/mount_union/mount_union.c	2011-08-29 16:35:03.000000000 +0200
--- sbin/mount_union/mount_union.c	2023-07-21 07:22:05.699670845 +0200
***************
*** 89,96 ****
  
  	mntflags = 0;
  	args.mntflags = UNMNT_ABOVE;
! 	while ((ch = getopt(argc, argv, "bo:")) != -1)
  		switch (ch) {
  		case 'b':
  			args.mntflags &= ~UNMNT_OPMASK;
  			args.mntflags |= UNMNT_BELOW;
--- 89,99 ----
  
  	mntflags = 0;
  	args.mntflags = UNMNT_ABOVE;
! 	while ((ch = getopt(argc, argv, "wbo:")) != -1)
  		switch (ch) {
+ 		case 'w':
+ 			args.mntflags |= UNMNT_FWRITE;
+ 			break;
  		case 'b':
  			args.mntflags &= ~UNMNT_OPMASK;
  			args.mntflags |= UNMNT_BELOW;