# Prevent TeX4ht from inserting img in equation with \mathcal

When I use TeX4ht to produce MathML, it produces an image when I use \mathcal in the equation. The result is that MathJax complains that the code is not valid. Is there a way to fix this problem?

Minimal working example, to be compiled with latex and tex4ht:

\documentclass{article}

\usepackage[xhtml,mathml]{tex4ht}

\begin{document}
$\mathcal{L}$
\end{document}

The resulting html file contains

<mi mathvariant="bold-script">
<img src="cmsy10-4c.png" alt="L" class="10x-x-4c" />
</mi>

How can I get rid of the img tag? And how come it is recognised as bold-script?

-