{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs";
    opam-nix.url = "github:tweag/opam-nix";
    flake-utils.url = "github:numtide/flake-utils";
    nixpkgs.follows = "opam-nix/nixpkgs";
  };
  outputs = { self, flake-utils, opam-nix, nixpkgs }@inputs:
    let package = "fixgen";
    in flake-utils.lib.eachDefaultSystem (system:
      let
        sourceRoot = ".";
        pkgs = nixpkgs.legacyPackages.${system};
        on = opam-nix.lib.${system};
        devPackagesQuery = {
          ocaml-lsp-server = "*";
          ocamlformat = "*";
          ocamlfind = "1.9.5";
          utop = "*";
        };
        query = devPackagesQuery // {
          ocaml-base-compiler = "*";
        };
        scope = on.buildOpamProject' { } ./. query;
        overlay = final: prev: {
          # You can add overrides here
          # Handles unpacker produced multiple directories error 
          timedesc-tzdb = prev.timedesc-tzdb.overrideAttrs (_: { sourceRoot = "."; });
          timedesc-tzlocal = prev.timedesc-tzdb.overrideAttrs (_: { sourceRoot = "."; });
          timedesc = prev.timedesc-tzdb.overrideAttrs (_: { sourceRoot = "."; });
          timedesc-sexp = prev.timedesc-tzdb.overrideAttrs (_: { sourceRoot = "."; });
          timere = prev.timedesc-tzdb.overrideAttrs (_: { sourceRoot = "."; });
          ${package} = prev.${package}.overrideAttrs (_: {
          });
        };
        scope' = scope.overrideScope' overlay;
        # The main package containing the executable
        main = scope'.${package};
        # Packages from devPackagesQuery
        devPackages = builtins.attrValues
          (pkgs.lib.getAttrs (builtins.attrNames devPackagesQuery) scope');
      in {
        legacyPackages = scope';

        packages.default = main;

        devShells.default = pkgs.mkShell {
          inputsFrom = [ main ];
          buildInputs = devPackages ++ [
          ];
        };
      });
}