diff -Naur busybox-1.17.4/include/usage.src.h busybox-1.17.4-magellan/include/usage.src.h
--- busybox-1.17.4/include/usage.src.h	2010-11-22 21:24:58.000000000 +0100
+++ busybox-1.17.4-magellan/include/usage.src.h	2011-07-01 17:47:51.000000000 +0200
@@ -4605,6 +4605,12 @@
      "\n	-r	Try to remount devices as read-only if mount is busy" \
      "\n	-l	Lazy umount (detach filesystem)" \
      "\n	-f	Force umount (i.e., unreachable NFS server)" \
+     "\n        -t vfstype" \
+     "\n               Indicate  that  the actions should only be taken on file systems" \
+     "\n               of the specified type. More than one type may be specified in" \
+     "\n               a comma separated list. The list of file system types can be" \
+     "\n               prefixed with 'no' to specify the file system types on which" \
+     "\n               no action should be taken" \
 	IF_FEATURE_MOUNT_LOOP( \
      "\n	-d	Free loop device if it has been used" \
 	)
diff -Naur busybox-1.17.4/util-linux/umount.c busybox-1.17.4-magellan/util-linux/umount.c
--- busybox-1.17.4/util-linux/umount.c	2010-11-22 21:24:58.000000000 +0100
+++ busybox-1.17.4-magellan/util-linux/umount.c	2011-07-01 17:30:31.000000000 +0200
@@ -56,7 +56,7 @@
 #endif
 
 /* ignored: -v -d -t -i */
-#define OPTION_STRING           "fldnra" "vdt:i"
+#define OPTION_STRING           "fldnrat:" "vdi"
 #define OPT_FORCE               (1 << 0)
 #define OPT_LAZY                (1 << 1)
 #define OPT_FREELOOP            (1 << 2)