anchor.diff:  }:
   
   stdenv.mkDerivation rec {
  -  name = "pngcrush-1.8.4";
  +  name = "pngcrush-1.8.5";
   
     src = fetchurl {
       url = "mirror://sourceforge/pmt/${name}-nolib.tar.xz";
  -    sha256 = "4ef6d790677cf57f622db693337d841b60d62c044e8681299245c298bd56161a";
  +    multihash = "QmbFB4XbmSyLSm6qYDtTrUo7DkR3u7iiNYsJqbiKswbqhr";
  +    allowHashOutput = false;
  +    sha256 = "1f843d836de8ef90b99b0a9e3e37f4ff4776278b5605293d5644b6efd537d934";
     };
   
     buildInputs = [
  
positive.code:     "ZINC=${zlib}/include"
      "ZLIB=${zlib}/lib"
    ];
  
    meta = with stdenv.lib; {
      description = "Portable Network Graphics (PNG) optimizing utility";
  
negative.code:     zlib
    ];
  
    postPatch = /* Fix hardcoded install prefix */ ''
      sed -i Makefile \
        -e "s,/usr,$out,"
    '';
  