Browser warning log: Could not find the language 'none'

If the AsciiDoc contains a [source] block without specifying a language, highlight.js prints a warning in the browser log:

Could not find the language 'none', did you forget to load/include a language module?
Falling back to no-highlight mode for this block.

The documentation explicitly describes this kind of usage for the [source] attribute:

When source is specified but a language isn’t specified in the attribute list of a source block or by the source-language document attribute, Antora applies the language none at runtime. The block is styled like other source blocks, but no syntax highlighting will be applied to its content.

Therefore, I would not expect a warning log on the generated page (with the Antora Default UI). Apologies if this is not the correct repository for this issue, as it could also be related to the Antora Default UI or even Asciidoctor.