stt latest version 1.4.0 fails to install

[Ferdev]

Nix newbie here. While trying to run a shell using this flake:

{
  inputs = {
    mach-nix.url = "mach-nix/3.5.0";
  };

  outputs = {self, nixpkgs, mach-nix }@inp:
    let
      l = nixpkgs.lib // builtins;
      supportedSystems = [ "x86_64-linux" "aarch64-darwin" ];
      forAllSystems = f: l.genAttrs supportedSystems
        (system: f system (import nixpkgs {inherit system;}));
    in
    {
      # enter this python environment by executing `nix shell .`
      defaultPackage = forAllSystems (system: pkgs: mach-nix.lib."${system}".mkPython {
        requirements = ''
          stt == 1.4.0
        '';
      });
    };
}

The installation fails with the following message:

error: builder for '/nix/store/c66r33dww5g0qiskbrgigrxdb2mdhn4h-mach_nix_file.drv' failed with exit code 1;
       last 10 log lines:
       > Mach-nix version: master
       > Python: 3.9.9
       > Cause: Requirements conflict: stt (<SpecifierSet('==1.4.0')>,)
       > The requirements which caused the error:
       >   stt (<SpecifierSet('==1.4.0')>,)
       >
       > The given requirements might contain package versions which are not yet part of the dependency DB
       > currently used. The DB can be updated by specifying 'pypiDataRev' when importing mach-nix.
       > For examples see: https://github.com/DavHau/mach-nix/blob/master/examples.md
       >
       For full logs, run 'nix log /nix/store/c66r33dww5g0qiskbrgigrxdb2mdhn4h-mach_nix_file.drv'.
(use '--show-trace' to show detailed location information)

I've cheked, and the latest pypi-deps-db includes stt@1.4.0. If I don't specify a version (== 1.4.0), it does install, but not the latest version. It installs 0.10.0-alpha.10 instead.

What am I doing wrong?

[TyberiusPrime]

You're not updating to the newest pypi-debs-db.
mach-nix defaults to a version of pypi-debs-db that was current when it was released.

You want something like this in your inputs:

inputs = {
    mach-nix = {
      url = "github:DavHau/mach-nix/3.5.0";
      inputs.pypi-deps-db.follows = "pypi-deps-db";
    };
    pypi-deps-db = {
      url = "github:DavHau/pypi-deps-db?rev=ba35683c35218acb5258b69a9916994979dc73a9";
      inputs.mach-nix.follows = "mach-nix";
    };

(or just define pyp-debs-dp without a rev, and rely on nix flake locking instead. The important part is to a) declare the input and b) have mach-nix 'follow' it. )