[ErrorException] Use of undefined constant username - assumed 'username'

<?php

class DatabaseSeeder extends Seeder {

/**
 * Run the database seeds.
 *
 * @return void
 */
public function run(){
    Eloquent::unguard();

    $this->call('UsersTableSeeder');
  }

}


class UsersTableSeeder extends Seeder {

public function run(){
    User::create([
        'username'  => 'Ziggy',
        'email'     => 'ziggy@stardust.com',
        'password'  =>  '1234'
    ]);
  }
}