Libreboot error: /boot/grub/i386-coreboot files not found

[白い熊＠相撲道]

I've installed and am running GuixSD on the Gluglug X200.

On boot, Libreboot comes up with its GRUB-like menu, where I select 
"Search for GRUB configuration on internal storage". It then finds the 
GuixSD partition with /boot/grub and you can boot it usinr "Load Config 
from (ahci0,msdosX)".

This then however always reports:

error: file `/boot/grub/i386-coreboot/vbe.mod' not found.
error: file `/boot/grub/i386-coreboot/vga.mod' not found.
error: file `/boot/grub/i386-coreboot/gfxterm.mod' not found.
Press any key to continue...

You can then hit a key and it continues normally, loads the GRUB menu 
and you can boot. So it's more of a nuisance than a crippling error. I'd 
like to get rid of it however.

Of course, there is no i386-coreboot in /boot/grub/, however symlinking 
i386-pc to it, or copying the dir i386-pc to i386-coreboot, has no 
effect. The error still comes up.

How can this be fixed?
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白い熊＠相撲道