Fetch remote nixpkgs with Kerberos auth

What do I need to do in order to get Nix to be able to fetch nixpkgs tarball from an URL that requires Kerberos auth?

I tried running nix-shell -I nixpkgs=<URL> -p <pkgs> but I kept gettting 401 unauthorised error. When I curled the URL in the command line it works fine.