No header when trying to configure static homepage with routes.yaml

I am using Ghost 2.22.1 with up-to-date Caspar Theme.

I am trying to configure a static homepage using following routes.yaml:

routes:
  /:
    data:
      post: page.home
    template: page

collections:

taxonomies:
  tag: /tag/{slug}/
  author: /author/{slug}/

So, I want to render a static site with slug home using the default page template. This works, somehow. But with default Caspar theme the menu is not rendered at all.

If I use Massively or London themes it renders perfectly.

Any help greatly appreciated, thank you!