I'm getting an error when trying to build a Guix system on the latest Guix revision (commit ea6594e08e2724c64bc07724a07479fc1633dede):
```
Backtrace:
1 (primitive-load "/root/.config/guix/current/bin/guix")
In guix/ui.scm:
1936:12 0 (run-guix-command _ . _)
guix/ui.scm:1936:12: In procedure run-guix-command:
In procedure %package-replacement-real: Wrong type argument:
#<inferior-package [email protected] 7f659c641150>
```
I can't find '%package-replacement-real' anywhere in the source.
