Extending Laravel Model

<?php

class Usuario extends Eloquent{
    public static $table = 'usuario';
    public static $timestamps = false;

    /**
     * Save the model instance to the database.
     *
     * @return bool
     */
    public function save(){

        if(isset($this->password))
            $this->password = Hash::make($this->password);

        Parent::save(); // Here fails
    }

    public static function validate($data){
        return Validator::make($data, array(
            'nome'      => 'required|min:3|max:80',
            'username'  => 'required|min:3|max:20',
            'password'  => 'required|min:6|max:20'
        ));
    }

}