Installation fails with poetry2nix error

I'm using NixOS 23.11 using flakes and home-manager. This is how I tried to set it up:

In configuration.nix:

{ config, pkgs, ... }:
{
  nixpkgs.overlays = [
    (import "${builtins.fetchTarball {url = "https://github.com/vlaci/openconnect-sso/archive/master.tar.gz"; sha256 = "08cqd40p9vld1liyl6qrsdrilzc709scyfghfzmmja3m1m7nym94";}}/overlay.nix")
  ];
}

In home.nix:

{ config, pkgs, ... }:
{
  home.packages = with pkgs; [
    openconnect-sso
  ];
}

$ sudo nixos-rebuild switch --impure
building the system configuration...
error:
       … while calling the 'head' builtin

         at /nix/store/w6qscasrm9g56nwgz9xv6nwcpcm2fjz8-source/lib/attrsets.nix:922:11:

          921|         || pred here (elemAt values 1) (head values) then
          922|           head values
             |           ^
          923|         else

       … while evaluating the attribute 'value'

         at /nix/store/w6qscasrm9g56nwgz9xv6nwcpcm2fjz8-source/lib/modules.nix:807:9:

          806|     in warnDeprecation opt //
          807|       { value = builtins.addErrorContext "while evaluating the option `${showOption loc}':" value;
             |         ^
          808|         inherit (res.defsFinal') highestPrio;

       (stack trace truncated; use '--show-trace' to show the full trace)

       error: poetry2nix is now maintained out-of-tree. Please use https://github.com/nix-community/poetry2nix/

I tried the flake before but it doesn't seem to work yet.

vlaci / openconnect-sso

Installation fails with poetry2nix error #157