error: while instantiating the derivation named `xmobar-0.8' at `/etc/nixos/nixpkgs/pkgs/applications/misc/xmobar/default.nix', line 5: while evaluating the derivation attribute `extraBuildInputs' at `/etc/nixos/nixpkgs/pkgs/applications/misc/xmobar/default.nix', line 8: attribute `X11' missing That was on nix-env -qas '*'