anchor.diff:  
   with stdenv.lib;
   let
  -  version = "0.20.1";
  +  version = "0.21.0";
     majorMinorVersion = versions.majorMinor version;
     desktop = fetchurl {
       url = "https://raw.githubusercontent.com/bitcoin-core/packaging/${majorMinorVersion}/debian/bitcoin-qt.desktop";
  
positive.code:     ++ optional withGui wrapQtAppsHook;
    buildInputs = [ boost zlib zeromq miniupnpc libevent ]
      ++ optionals stdenv.isLinux [ util-linux ]
      ++ optionals withWallet [ db48 ]
      ++ optionals withGui [ qtbase qttools qrencode ];
  
    postInstall = optional withGui ''
  
negative.code:       "https://bitcoincore.org/bin/bitcoin-core-${version}/bitcoin-${version}.tar.gz"
        "https://bitcoin.org/bin/bitcoin-core-${version}/bitcoin-${version}.tar.gz"
      ];
      sha256 = "1a91202c62ee49fb64d57a52b8d6d01cd392fffcbef257b573800f9289655f37";
    };
  
    nativeBuildInputs =
  