anchor.diff:    pythonPackages = python27Packages;
   in stdenv.mkDerivation rec {
     name = "freecad-${version}";
  -  version = "0.17";
  +  version = "0.18.1";
   
     src = fetchurl {
       url = "https://github.com/FreeCAD/FreeCAD/archive/${version}.tar.gz";
  -    sha256 = "1yv6abdzlpn4wxy315943xwrnbywxqfgkjib37qwfvbb8y9p60df";
  +    sha256 = "0lamrs84zv99v4z7yi6d9amjmnh7r6frairc2aajgfic380720bc";
     };
   
     buildInputs = [ cmake coin3d xercesc ode eigen qt4 opencascade gts
  
positive.code:   ] ++ (with pythonPackages; [
      matplotlib pycollada pyside pysideShiboken pysideTools pivy python boost
    ]);
  
    patches = [
      # Fix for finding boost_python. Boost >= 1.67.0 appends the Python version.
      (fetchpatch {
        url = https://github.com/FreeCAD/FreeCAD/commit/3c9e6b038ed544e446c61695dab62f83e781a28a.patch;
        sha256 = "0f09qywzn0y41hylizb5g8jy74fi53iqmvqr5zznaz16wpw4hqbp";
      })
    ];
  
    enableParallelBuilding = true;
  
  
negative.code:   postInstall = ''
      wrapProgram $out/bin/FreeCAD --prefix PYTHONPATH : $PYTHONPATH \
        --set COIN_GL_NO_CURRENT_CONTEXT_CHECK 1
    '';
      
    meta = with stdenv.lib; {
      description = "General purpose Open Source 3D CAD/MCAD/CAx/CAE/PLM modeler";
      homepage = https://www.freecadweb.org/;
  