Nix shell on nix-darwin w/ flakes

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1

I’ve got a flakes based nix-darwin set up.

My inputs are set up like this:

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/release-24.05";
    nix-darwin = {
      url = "github:LnL7/nix-darwin";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    home-manager = {
      url = "github:nix-community/home-manager/release-24.05";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

Then I add nix packages to the path:

      nix.nixPath = [
        { nixpkgs = "${pkgs.path}"; }
        { nixos-config = "${toString ./flake.nix}"; }
        { darwin-config = "$HOME/.nixpkgs/darwin-configuration.nix"; }
      ];

Following the advice from this thread: Correct way to use <nixpkgs> in nix-shell on flake-based system without channels

and finally a shell file

with (import <nixpkgs> {});
mkShell {
    buildInputs = [
      python312
      pdm
      mariadb
    ];
  }

However, when I create a shell and install the pdm package, I’m getting version 2.10. When I check the version in nix packages on git it should be 2.15. Is there something I’m missing? I did recently upgrade the nix packages release from 23.11 to 24.05.