yii2 user register without email

Hi, i am using yii2 basic with module dektrium yii2 user.

I want to remove email requirement when registration.

I alredy extend the class dektrium\user\models\RegistrationForm and do this in the class

public function rules()


        $rules = parent::rules();


        return $rules;


Now there is no warning when i dont fill in email, but the registration fail. The page just showing loading icon for a while, then nothing happen.

Please help.