Describe the issue

In CSS, custom property such as --_margin-top: 1rem, top gets wrongly highlighted

It seems to be caused by some kind of interaction between the underscore and hyphen.

Which language seems to have the issue?

CSS, I'm using language="css" and NOT using auto-detect.

Sample Code to Reproduce

.example {
    --_margin-top: 1rem;
}

Expected behavior

--_margin-top should be treated as an atomic unit of text for highlighting purposes.