How can I get Emacspeak-60 with overlays?

I’m trying to build Emacspeak-60, as only 59 is available.

I do:

  nixpkgs.overlays = [
(self: super: {
  emacsPackages = super.emacsPackages // {
    emacspeak = super.emacsPackages.emacspeak.overrideAttrs (oldAttrs: rec {
      src = self.fetchgit {
        url = "https://github.com/tvraman/emacspeak.git";
        rev = "60.0";
        sha256 = "0sjjj9z1dhilhpc8pq4154czrb79z9cm044jvn75kxcjv6v5l2m5";
      };
    });
  };
})
    (self: super: {
      emacsWithConfig = super.emacsWithPackages (epkgs:
        (with epkgs.melpaPackages; [
          self.emacsPackages.emacspeak
        ])
      );
    })
  ];

, but I get:

building '/nix/store/6dwscj1rpblzkrk9r9xqphrckrabfpnr-etc-current-system-packages.drv'...
building '/nix/store/7q0wh1d43khzdxlgylhdz2jynf91yn26-emacspeak.drv'...
exporting https://github.com/tvraman/emacspeak.git (rev 60.0) into /nix/store/2pbzrkp5c3hq9cg9brgpl6h9i9yq36gl-emacspeak
Initialized empty Git repository in /nix/store/2pbzrkp5c3hq9cg9brgpl6h9i9yq36gl-emacspeak/.git/
remote: Enumerating objects: 1716, done.
remote: Counting objects: 100% (1716/1716), done.
remote: Compressing objects: 100% (1450/1450), done.
remote: Total 1716 (delta 458), reused 926 (delta 206), pack-reused 0 (from 0)
Receiving objects: 100% (1716/1716), 97.66 MiB | 11.94 MiB/s, done.
Resolving deltas: 100% (458/458), done.
From https://github.com/tvraman/emacspeak
 * tag               60.0       -> FETCH_HEAD
Switched to a new branch 'fetchgit'
removing `.git'...
error: hash mismatch in fixed-output derivation '/nix/store/7q0wh1d43khzdxlgylhdz2jynf91yn26-emacspeak.drv':
         specified: sha256-pQpattmS9VmO3ZIQUFn66az8GSmB4IvYhTTCFn6SUmo=
            got:    sha256-0HV2xi2QXDeE20iJmUMSOpGvi7hAV7jxuph3SCdOPts=
error: 1 dependencies of derivation '/nix/store/87jyapy10abibqn2z4y310x6w9mhbcmk-emacspeak-59.0.drv' failed to build
error: 1 dependencies of derivation '/nix/store/znqgirrcpbvavqs45gj8naxn8ciikbkg-emacs-with-packages-29.3.drv' failed to build
error: 1 dependencies of derivation '/nix/store/jsnkxaiv90fl8aba1d55wm7x146pgw2q-system-path.drv' failed to build
error: 1 dependencies of derivation '/nix/store/02nzgv325jijx08z2wvyh04h01sy6639-nixos-system-quasar-24.05.2310.7dca15289a1c.drv' failed to build