anchor.diff:      ++ stdenv.lib.optional faacSupport faac
       ++ stdenv.lib.optional flacSupport flac
       ++ stdenv.lib.optional soxSupport sox
  -    ++ stdenv.lib.optional vorbisSupport vorbisTools;
  +    ++ stdenv.lib.optional vorbisSupport vorbis-tools;
   
     # upstream has no tests
     checkPhase = ''
  
positive.code: , faacSupport ? false, faac ? null
  , flacSupport ? true, flac ? null
  , soxSupport ? true, sox ? null
  , vorbisSupport ? true, vorbisTools ? null
  }:
  
  assert mp3Support -> lame != null;
  
negative.code: assert faacSupport -> faac != null;
  assert flacSupport -> flac != null;
  assert soxSupport -> sox != null;
  assert vorbisSupport -> vorbis-tools != null;
  
  let
    zeroconf = pythonPackages.callPackage ./zeroconf.nix { };
  