UFS Mounting UFS partition with equal to already mounted label - fails with an error.

[hishnik]

Hello.
I'm trying to convert my boot drive to UEFI and found one problem.
Boot partition at old disk should have the same UFS label as at new one.

For example it would be `myufsboot`.

So da0p2 has this label and mounted to some place on filesystem to make /boot point there.
And da1p2 has same label and can not be mounted, even by partition name.

root@hostname:/ # mount /dev/da1p2 /mnt/disk0
mount: /dev/da1p2: Operation not permitted

what can we do here?