Latest issue trying to organize my Guix configuration files -> error: Unknown command: hostname

Guix
1

Still following this tutorial, I run into yet another issue:

$ test-home
fish: Unknown command: hostname
~/.config/fish/config.fish (line 1): 
hostname
^~~~~~~^
in command substitution
	called on line 33 of file ~/.config/fish/config.fish
from sourcing file ~/.config/fish/config.fish
	called during startup
~/.config/fish/config.fish (line 33): Unknown command
alias test-home "sudo guix home -L ~/dotfiles container ~/dotfiles/config/home/folaht/$(hostname).scm"
                                                                                       ^~~~~~~~~^