Index: /trunk/src/VBox/Additions/linux/installer/vboxadd.sh
===================================================================
--- /trunk/src/VBox/Additions/linux/installer/vboxadd.sh	(revision 80566)
+++ /trunk/src/VBox/Additions/linux/installer/vboxadd.sh	(revision 80567)
@@ -528,5 +528,7 @@
     fi
     if ! umount -a -t vboxsf 2>/dev/null; then
-        fail "Cannot unmount vboxsf folders"
+	# Make sure we only fail, if there are truly no more vboxsf
+	# mounts in the system.
+	[ -n "$(findmnt -t vboxsf)" ] && fail "Cannot unmount vboxsf folders"
     fi
     test -n "${INSTALL_NO_MODULE_BUILDS}" ||