command and error

[root@nixkm:~]# nixos-rebuild switch --upgrade
unpacking channels...
building Nix...
building the system configuration...
error: value is a list while a set was expected, at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:257:62
(use '--show-trace' to show detailed location information)

[root@nixkm:~]#