Issues installing via nix flake

[am-on]

With the following flake.nix

{
  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.11";
  inputs.nixpkgs-unstable.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
  inputs.paretosecurity.url = "github:paretosecurity/pareto-linux";

  outputs =
    { self
    , nixpkgs
    , nixpkgs-unstable
    , paretosecurity
    ,
    }:

    let
      system = "x86_64-linux";

      overlay-unstable = final: prev: {
        unstable = import nixpkgs-unstable {
          inherit system;
          config.allowUnfree = true;
        };
      };

      overlayModules = [
        (
          { config, pkgs, ... }:
          {
            nixpkgs.overlays = [
              overlay-unstable
            ];
          }
        )
      ];

      pareto = [
        paretosecurity.nixosModules.default
        {
          environment.systemPackages = [ paretosecurity.packages.${system}.default ];
        }
      ];

    in
    {
      # change `yourhostname` to your actual hostname
      nixosConfigurations.nixos = nixpkgs.lib.nixosSystem {
        # change to your system:
        system = "x86_64-linux";
        modules = overlayModules ++ pareto ++ [ ./configuration.nix ];
      };
    };
}

I get this error:

       error: undefined variable 'mkOption'
       at /nix/store/fklqw8fr9fdkdj4shfxaiji78i3w99c9-source/modules/paretosecurity.nix:7:46:
            6| }: {
            7|   options.paretosecurity.paretosecurityBin = mkOption {
             |                                              ^
            8|     type = types.str;