#<unspecified> returned among (devices)

Hello,

On a particular machine, where 'p devices' in parted returns:

/dev/sda (500GB)
/dev/sdb (512GB)
/dev/sdc (1000GB)
/dev/sdd (8053MB)
/dev/nvme0n1 (1000GB)

Then, at the Guile REPL:

scheme@(guix-user)> ,import (parted)
scheme@(guix-user)> (probe-all-devices!)
$2 = 25
scheme@(guix-user)> (devices)
$3 = (#<<device> bytestructure: #<bytestructure 0x7f371532a810>> #<<device> bytestructure: #<bytestructure 0x7f371532a7b0>> #<<device> bytestructure: #<bytestructure 0x7f371532a750>> #<<device> bytestructure: #<bytestructure 0x7f371532a6f0>> #<<device> bytestructure: #<bytestructure 0x7f371532a690>>)
scheme@(guix-user)> (map device-type $3)
$4 = (device-type-scsi device-type-scsi device-type-scsi device-type-scsi #<unspecified>)

As a consequence, the Guix installer is broken, attempting to manipulate strings at some point and instead getting #<unspecified>.

/dev/sdc and /dev/nvme0n1 appear to be the same drive on this UEFI system.