how to apply where condition in the result that we got from relationship in laravel code example

Example: laravel adding condition to relation

class Game extends Eloquent {
    // many more stuff here

    // relation without any constraints ...works fine 
    public function videos() {
        return $this->hasMany('Video');
    }

    // results in a "problem", se examples below
    public function available_videos() {
        return $this->videos()->where('available','=', 1)->get();
    }
}