Thymol munges XHTML documents?

[tjdownes]

It appears that Thymol may remove self-closing slash on void elements, including for XHTML documents. This causes XHTML documents to fail validation. This is important because we use the HTML compiled by the Thymol server to perform validation on Thymeleaf templates before allowing the backend to use them on their Spring server, and therefore must pass validation tests.

I believe the problem actually exists within the jsdom package, and may be related to this issue:
jsdom/jsdom#798