Laravel: SoftDeletes doesnt work when I add $appends field

I have a model with softdeletes, if I add A appends field my sofdeletes implementation doesnt work, somebody knows what is happend?

use Illuminate\Database\Eloquent\Model;

use Illuminate\Database\Eloquent\SoftDeletes;

class Users extends Model
{
    use SoftDeletes;

    protected $dates = ['deleted_at'];

    protected $table = 'users';

    protected $appends = ['assigned'];

    protected $fillable = ['category_id'];

    public function __construct()
    {
        $this->assigned = false;
    }

    public function setAssignedAttribute($value)
    {
        $this->attributes['assigned'] = $value;
    }

    public function getAssignedAttribute($value)
    {
        return $value;
    }
}

via user1470098