{
packageOverrides = pkgs: {
unison = (pkgs.unison.override {
ocaml = pkgs.ocaml_4_02;
enableX11 = false;
}).overrideDerivation (oldAttrs: {
src = pkgs.fetchurl {
url = "http://www.seas.upenn.edu/~bcpierce/unison/download/releases/unison-2.49.543/unison-2.49.543.tar.gz";
sha512 = "3kg1vic15vi5qhczjxd8h69ibs188hcfb882hcmprwqz22dw48b4frwjwvdiwa02byxjqc26zsalz490m3yrmc6rzalgpgx1bwbrvzw";
};
});
};
}