anchor.diff:      optionals
       optionalString;
   
  -  mumble-theme = stdenv.mkDerivation {
  -    name = "mumble-theme-2017-11-26";
  -
  -    src = fetchFromGitHub {
  -      version = 5;
  -      owner = "mumble-voip";
  -      repo = "mumble-theme";
  -      rev = "212f8e336d3c2b385c10a7462ceedb88919edd00";
  -      sha256 = "fca086c622b6cde4530647b5c3fa7b05e50adfdbb99705df54efbc6c18668b7f";
  -    };
  -
  -    installPhase = ''
  -      mkdir -pv "$out"
  -      cp -rv . $out/
  -    '';
  +  mumble-theme = fetchFromGitHub {
  +    version = 5;
  +    owner = "mumble-voip";
  +    repo = "mumble-theme";
  +    rev = "212f8e336d3c2b385c10a7462ceedb88919edd00";
  +    sha256 = "fca086c622b6cde4530647b5c3fa7b05e50adfdbb99705df54efbc6c18668b7f";
     };
   
     celt_mumble-src = fetchFromGitHub {
  
positive.code:     mv -v 3rdparty/qqbonjour-src/ 3rdparty-new/
      mv -v 3rdparty/smallft-src/ 3rdparty-new/
  
      # Remove original 3rdparty directory to ensure vendored sources are
      # not used.
      rm -rv 3rdparty
      mv -v 3rdparty-new 3rdparty
  
negative.code:       mv -v "$celt_unpack_dir" celt-0.7.0-src/
      popd
  
      pushd themes/
        unpackFile '${mumble-theme}'
        mumble_theme_unpack_dir="$(
          find . -type d -regextype sed -regex '\./mumble-theme-[a-z0-9]\{40\}'
        )"
        mv -v "$mumble_theme_unpack_dir"/* Mumble/
      popd
    '' + optionalString (config == "murmur" && ice != null) ''
      sed -i 's,/usr,${ice},g' src/murmur/murmur_ice/murmur_ice.pro
    '' + ''
  