final: prev: {
  berkeley-mono = prev.stdenvNoCC.mkDerivation {
    pname = "berkeley-mono";
    version = "1.0";
    src = ../modules/system/berkeley-mono;
    installPhase = ''
      install -Dm644 *.ttf \
        -t $out/share/fonts/truetype/berkeley-mono
    '';
  };
}