{
  inputs = {
    nixpkgs = {
      url = "github:NixOS/nixpkgs/nixpkgs-unstable";
    };
    utils.url = "github:numtide/flake-utils";
    haskellNix.url = "github:input-output-hk/haskell.nix";

  };

  outputs =
    inputs:
    inputs.utils.lib.eachDefaultSystem (
      system:
      let
        pkgs = import inputs.nixpkgs {
          localSystem = system;
          overlays = [
            inputs.haskellNix.overlay
            (_: prev: {
              riscv-formal = prev.callPackage (
                {
                  haskell-nix,
                  qemu,
                }:
                haskell-nix.hix.project {
                  compiler-nix-name = "ghc966";
                  src = builtins.path {
                    path = ./.;
                    name = "riscv-formal-source";
                  };
                  shell =
                    let
                      riscv64-linux = prev.pkgsCross.riscv64-embedded.__splicedPackages;
                      # Everything here builds and runs without needing the below crossSystem
                      #riscv64-linux = (import prev.pkgs.path {
                      #  localSystem = system;
                      #  crossSystem = {

                      #    config = "riscv64-none-elf";
                      #    libc = "newlib";
                      #    gcc = {
                      #      # Both sets work to build and run hello_world
                      #      # This matches what is in the makefile
                      #      #arch = "rv64ima";
                      #      #abi = "lp64";
                      #      # This matches what you asked for on matrix
                      #      #arch = "rv64g";
                      #      #abi = "lp64d";
                      #    };
                      #  };
                      #}).__splicedPackages;
                    in
                    {
                      tools = {
                        cabal = { };
                        hlint = { };
                      };
                      nativeBuildInputs = [
                        qemu
                        riscv64-linux.gcc
                        riscv64-linux.binutils
                      ];
                      buildInputs = [
                        riscv64-linux.glibc
                      ];
                      shellHook = ''
                        export CROSS_PREFIX="riscv64-none-elf"
                      '';
                    };
                }
              ) { };
            })
          ];
        };
        flake = pkgs.riscv-formal.flake { };
      in
      flake
    );

  nixConfig = {
    # https://input-output-hk.github.io/haskell.nix/tutorials/getting-started-flakes.html#setting-up-the-binary-cache
    extra-substituters = [ "https://cache.iog.io" ];
    extra-trusted-public-keys = [ "hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=" ];
    allow-import-from-derivation = true;
  };
}