The error:

root@guix ~# guix system reconfigure /etc/config.scm
The following derivation will be built:
   /gnu/store/g26kkrfd49y5wcz57x0xgkh97w997kmb-grub.cfg.drv
building /gnu/store/g26kkrfd49y5wcz57x0xgkh97w997kmb-grub.cfg.drv...
/gnu/store/2lnjrv5388727sw45jhrrsyf0140nrd2-system
/gnu/store/gsxap47dgsjs6zvdim42j5lal5rfj10w-grub.cfg

activating system...
making '/gnu/store/2lnjrv5388727sw45jhrrsyf0140nrd2-system' the current system...
setting up setuid programs in '/run/setuid-programs'...
populating /etc from /gnu/store/hzhhbayyfxjqghxklawy8r8a1i8ws7pg-etc...
The following derivation will be built:
   /gnu/store/6wy32ybajjrdn1nydvp1i0iai6x77jqc-install-bootloader.scm.drv
building /gnu/store/6wy32ybajjrdn1nydvp1i0iai6x77jqc-install-bootloader.scm.drv...
guix system: bootloader successfully installed on '/dev/sda'
guix system: error: exception caught while executing 'eval' on service 'root':
Unrecognized keyword: #:file-creation-mask