Generate relative longdesc on <img>?

Hello,

What HTML customization serves to get relative paths in the longdesc attribute on img elements?

The longdesc links and pages are fine, so it's not something noticeable when browsing. But img elements in HTML are coming out with absolute paths in longdesc attributes.

For example:

<img src="" longdesc="">

The corresponding source for the whole media object is:

   <mediaobject xml:id="figure-standalone-repl">

    <alt>Dedicated servers versus consolidated instances</alt>

    <imageobject>

     <imagedata fileref="images/standalone-repl.png" format="PNG"/>

    </imageobject>

    <textobject>

     <para>Dedicated servers are suited to environments with large numbers

     of replicas.</para>

    </textobject>

   </mediaobject>

Regards,

Mark