Double binds /mnt/{proc,sys,dev} on -current installer

Installer mount target partition at /mnt. Then creates chroot environment. Mount command lists each /mnt/proc , /mnt/sys, /mnt/dev/ twice. And it is not only listing. To unbind /mnt/proc you need run this
Code:# umount /mnt/proc
# umount /mnt/proc
umount: /mnt/proc: not mounted.also twice. For me something is wrong here.