Changing keyboard layout to type the password to decipher the root file system at boot

I changed the physical keyboard of a laptop to have a different layout. I changed the keyboard layout accordingly in Mate, it works fine.

However, Trisquel 10 was installed with LVM and ciphering (default options of the Trisquel 10 graphic installer, it makes an unciphered /boot partition and root/swa/home in ciphered partion), and at boot, when I type the password, if I assume the new layout it does not work, it only works with the old layout.

How can I change the keyboard layout to type the password for deciphering the root file system at boot?