public function replace($id, ItemInterface $newItem)
    {
        $success = false;
        foreach ($this->items as $i => $item) {
            if ($item->getFeedId() == $id) {
                $this->items[$i] = $newItem;
                $success = true;
                break;
            }
        }

        if (false === $success) {
            throw new \InvalidArgumentException('Unknown item');
        }

        return $this;
    }