DOCBOOK-APPS: docbook-xsl and textdata fileref

Hi,

upon a suggestion by norman I tried the following with docbook xsl v1.53:

<programlisting><textobject>
<textdata fileref="pathtoprogramlisting"/>
</textobject>
</programlisting>

the fileref does not seem to be resolved and I do not get any text output?

I'm using xml parser/xslt processor bundled with jdk1.4 and ant's style task.

is this feature not yet implemented in docbook-xsl or is this a problem with 
my local setup?

thanks in advance,

robert