Problem z botem do Discord'a

const commando = require('discord.js-commando');

class DiceRollCommand extends commando.Command
{
  constructor(client)
  {
    super(client,{
      name: 'roll',
      gropu: 'random',
      memberName: 'roll',
      description: 'rolls a die'
    });

  }
  async run(message, args)
  {
    var roll = Math.floor(Math.random() * 6) + 1;
    message.reply("You rolled a: " + roll);
  }
}



module.exports = DiceRollCommand;

błąd: 

TypeError: Command group must be a string.
    at DiceRollCommand.Command (C:\Users\Piotr\Desktop\Bot\node_modules\discord.js-commando\src\commands\base.js:59:44)
    at DiceRollCommand (C:\Users\Piotr\Desktop\Bot\commands\random\dice_roll.js:7:5)
    at CommandRegistry.registerCommands (C:\Users\Piotr\Desktop\Bot\node_modules\discord.js-commando\src\registry.js:114:48)
    at CommandRegistry.registerCommandsIn (C:\Users\Piotr\Desktop\Bot\node_modules\discord.js-commando\src\registry.js:166:15)
    at Object.<anonymous> (C:\Users\Piotr\Desktop\Bot\index.js:8:14)
    at Module._compile (module.js:569:30)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:503:32)
    at tryModuleLoad (module.js:466:12)
    at Function.Module._load (module.js:458:3)