anchor.diff:  }:
   
   let
  -  version = "3.4.0";
  +  version = "3.4.1";
   
     src = fetchFromGitHub {
       owner  = "opencv";
       repo   = "opencv";
       rev    = version;
  -    sha256 = "1nc14kvsjwaisv7d1r6f0hn7na9zr2cm2zh3hd3r9qwm3g78xnac";
  +    sha256 = "08yahgf427d2qbs2mw02xww6bv5yjkfc1hihihh7fhqgfz0jnj1h";
     };
   
     contribSrc = fetchFromGitHub {
       owner  = "opencv";
       repo   = "opencv_contrib";
       rev    = version;
  -    sha256 = "1cxw7nra3f1hng057c6hi1ynsyqdazd69irjdgn8xjg6q9h76br0";
  +    sha256 = "00x1x53qv2pnc7i56244b5nf44wm2mp77hj486i5697r6hikk8n3";
     };
   
     # Contrib must be built in order to enable Tesseract support:
  
positive.code:     "-DOPENCV_ENABLE_NONFREE=${printEnabled enableUnfree}"
      "-DBUILD_TESTS=OFF"
      "-DBUILD_PERF_TESTS=OFF"
      (opencvFlag "IPP" enableIpp)
      (opencvFlag "TIFF" enableTIFF)
      (opencvFlag "JASPER" enableJPEG2K)
  
negative.code: stdenv.mkDerivation rec {
    name = "opencv-${version}";
    inherit version src;
  
    postUnpack = lib.optionalString buildContrib ''
      cp --no-preserve=mode -r "${contribSrc}/modules" "$NIX_BUILD_TOP/opencv_contrib"
  