Bad parameter to boot GuixSD in a VM

[良ϖ]

Hi,

I've followed instructions on this page:
https://www.gnu.org/software/guix/manual/html_node/Installing-GuixSD-in-a-VM.html

Howeverpoint 3 ("Boot the USB installation image in an VM: ") gets:

qemu-system-x86_64: -net default: Invalid parameter 'default'

If I remove that parameter I get another error:

WARNING: Image format was not specified for
'guixsd-usb-install-0.12.0.x86_64-linux' and probing guessed raw.
         Automatically detecting the format is dangerous for raw
images, write operations on block 0 will be restricted.
         Specify the 'raw' format explicitly to remove the restrictions.

Any ideas how I could solve that? Thanks in advance,

piotr