Panel error Page::previewUrl

I’m not sure, if this is intended or a bug, so I’m asking here first, before opening an issue on github.

I’ve set up a page blueprint with the following options:

    *: false
    admin: true

the preview option throws an error, because it’s obviously an array that I’m passing in:
Kirby\Cms\Page::previewUrl(): Return value must be of type ?string, array returned

If I set preview: false, it’s working correctly.

Thanks in advance!

Forgot to mention the kirby version: