Erik Hetzner <egh@e6h.org> writes:

> In emacs 26.3, the entire heading line (and block delimiter) has a background color. In emacs 27, this is not the case.
>
> See attached images.

With the attached diff against leuven, running

    emacs -Q -l $your_elisp_snippet $your_org_file

yields this (with commit d453cee177 on emacs-27):