anchor.diff:  , libxml2, libxslt, makeWrapper, p7zip, xar, gzip, cpio }:
   
   let
  -  version = "1.8.7";
  +  version = "1.9.1";
     rake = buildRubyGem {
       inherit ruby;
       gemName = "rake";
  
positive.code: 
    preFixup = ''
      # 'hide' the template file from shebang-patching
      chmod -x "$out/opt/vagrant/embedded/gems/gems/bundler-1.12.5/lib/bundler/templates/Executable"
      chmod -x "$out/opt/vagrant/embedded/gems/gems/vagrant-$version/plugins/provisioners/salt/bootstrap-salt.sh"
    '';
  
    postFixup = ''
      chmod +x "$out/opt/vagrant/embedded/gems/gems/bundler-1.12.5/lib/bundler/templates/Executable"
      chmod +x "$out/opt/vagrant/embedded/gems/gems/vagrant-$version/plugins/provisioners/salt/bootstrap-salt.sh"
    '' +
    (stdenv.lib.optionalString stdenv.isDarwin ''
  
negative.code:       else "system ${stdenv.system} not supported";
  
    sha256 = {
      "x86_64-linux"  = "0l1if9c4s4wkbi8k00pl7x00lil21izrd8wb9nv2b5q4gqidc1nh";
      "i686-linux"    = "1789wjwcpgw3mljl49c8v5kycisay684gyalkkvd06928423y9zb";
      "x86_64-darwin" = "1xrfq1a0xyifkhhjnpm6wsnms9w8c9q5rd2qqn4sm5npl7viy68p";
    }."${stdenv.system}" or (throw "system ${stdenv.system} not supported");
  
    arch = builtins.replaceStrings ["-linux"] [""] stdenv.system;
  