Scout not paginating after defining custom toSearchableArray

I have a Post and a Category model. Each post can have many categories.

I'm trying to set my search so the keyword will be searched on posts and on its categories.

I achieved this by writing a custom toSearchableArray method on my Post model, but now my pagination is gone.

Here's the method

    public function toSearchableArray()
    {
        $array = $this->toArray();
        $array['categories'] = $this->categories;

        return $array;
    }

And here's how I'm calling it on the Controller

            return Post::search($request->search)->paginate(2)->load('categories');

Any ideas on how I could solve this?