docbookk xml -> html looses language attribute

hi,

this docbook

<informalexample>
  <programlisting language="c">...</programlisting>
</informalexample>

will be converted to this html:

<div class="informalexample">
  <pre class="programlisting">...</pre>
</div>

This looses the language="c" information. How would one 'fix' that. I can
probably handle this in the customization layer. I guess using the lang
attribute of pre is out of question (should probably be used for spoken
languages). What other option would you suggest:

<div class="informalexample">
  <pre class="programlisting" ><code class="c">...</code></pre>
</div>

<div class="informalexample">
  <div class="programlisting" ><pre class="c">...</pre></div>
</div>

... I need the information as I post process the generated HTML to get syntax
highlighting (I am using xsltproc and there it does not work for known reasons).

Stefan