On Guix commit 763b52dc54a5732d014ffaecba45125e9f38ed35
I get this error when reconfiguring my system:

--8<---------------cut here---------------start------------->8---
[...]
building /gnu/store/wd1fj9n65xpdf22bzlswi6rk166miznh-install-bootloader.scm.drv...
guix system: bootloader successfully installed on '/dev/sdb'
The following derivation will be built:
   /gnu/store/4b7pizn41jq8aayqban639c7xddby29w-upgrade-shepherd-services.scm.drv
building /gnu/store/4b7pizn41jq8aayqban639c7xddby29w-upgrade-shepherd-services.scm.drv...
guix system: error: exception caught while executing 'start' on service 'file-system-/sys/kernel/debug':
Throw to key `match-error' with args `("match" "no matching pattern" ("none" "/sys/kernel/debug" "debugfs" () #f #f #f))'.
--8<---------------cut here---------------end--------------->8---

The system reboots properly.

-- 
Pierre Neidhardt
https://ambrevar.xyz/