nix build results in "failed to create symbolic link"

[SebastianStork]

I followed the instructions for the "Using as a nixos-module" method. My configuration can be found here.

When I run nix build .#nixosConfigurations.installer.config.formats.iso I get this error:

error: builder for '/nix/store/0acylkkqsd9q36gzdqwibc1337jhwfhd-NixOS.iso.drv' failed with exit code 1;
       last 10 log lines:
       > sourcing setup hook '/nix/store/fyaryjvghbkpfnsyw97hb3lyb37s1pd6-move-lib64.sh'
       > sourcing setup hook '/nix/store/kd4xwxjpjxi71jkm6ka0np72if9rm3y0-move-sbin.sh'
       > sourcing setup hook '/nix/store/pag6l61paj1dc9sv15l7bm5c17xn5kyk-move-systemd-user-units.sh'
       > sourcing setup hook '/nix/store/jivxp510zxakaaic7qkrb7v1dd2rdbw9-multiple-outputs.sh'
       > sourcing setup hook '/nix/store/ilaf1w22bxi6jsi45alhmvvdgy4ly3zs-patch-shebangs.sh'
       > sourcing setup hook '/nix/store/cickvswrvann041nqxb0rxilc46svw1n-prune-libtool-files.sh'
       > sourcing setup hook '/nix/store/xyff06pkhki3qy1ls77w10s0v79c9il0-reproducible-builds.sh'
       > sourcing setup hook '/nix/store/aazf105snicrlvyzzbdj85sx4179rpfp-set-source-date-epoch-to-latest.sh'
       > sourcing setup hook '/nix/store/gps9qrh99j7g02840wv5x78ykmz30byp-strip.sh'
       > ln: failed to create symbolic link '/nix/store/2yx7pj2gy89fj1m6vcvcd0j358hrd7bs-NixOS.iso' -> '': No such file or directory
       For full logs, run 'nix log /nix/store/0acylkkqsd9q36gzdqwibc1337jhwfhd-NixOS.iso.

The same happens when I append -o result to specify the symlink location.

Is this intended behavior? I couldn't find any other mention of this anywhere. Any help is appreciated.