NixOS User Creation Error

# partial contents of: /etc/nixos/configuration.nix
{
  ...
  # created this nixos from this stock vagrant box: https://github.com/zimbatm/nixbox
  users = {
    extraGroups = [ { name = "vagrant"; } { name = "twashing"; } { name = "vboxsf"; } ];
    extraUsers  = [ {
      description     = "Vagrant User";
      name            = "vagrant";
      ...
    }
    { description     = "Main User";
      name            = "user1";
      group           = "user1";
      extraGroups     = [ "users" "vboxsf" "wheel" "networkmanager"];
      home            = "/home/user1";
      createHome      = true;
      useDefaultShell = true;
    } ];
  };
  ...
}

# errors when trying to rebuild environment
$ sudo nixos-rebuild switch

building Nix...
building the system configuration...
updating GRUB 2 menu...
stopping the following units: local-fs.target, network-interfaces.target, remote-fs.target
activating the configuration...
setting up /etc...
useradd: group 'networkmanager' does not exist
chpasswd: line 1: user 'user1' does not exist
chpasswd: error detected, changes ignored
id: user1: no such user
id: user1: no such user
/nix/store/1r443r7imrzl4mgc9rw1fmi9nz76j3bx-nixos-14.04.393.6593a98/activate: line 77: test: 0: unary operator expected
chown: missing operand after ‘/home/user1’
Try 'chown --help' for more information.
/nix/store/1r443r7imrzl4mgc9rw1fmi9nz76j3bx-nixos-14.04.393.6593a98/activate: line 78: test: 0: unary operator expected
chgrp: missing operand after ‘/home/user1’
Try 'chgrp --help' for more information.
starting the following units: default.target, getty.target, ip-up.target, local-fs.target, multi-user.target, network-interfaces.target, network.target, paths.target, remote-fs.target, slices.target, sockets.target, swap.target, timers.target