Strange fop behavior with last page anchor

["Luciano Scavizzi" <feanorelf@gmail.com>]

Hallo.
I am using FOP 0.92b as a FO-Processor, and I am trying to output a
"page  / total-pages" footer.

If I use, as <para> a reference for the last page, that is:

<para id="biblioid_theEnd"/>

the file is processed as I expect, but if I use an anchor, i.e.

<anchor id="biblioid_theEnd"/>,

for each processed page, FOP gives the following warning:
21-giu-2006 15.00.18 org.apache.fop.area.RenderPagesModel checkPreparedPages
AVVERTENZA: Page 1: Unresolved id reference "PA601_theEnd" found.

Now I am working with <para>s, but I don't like the idea of using a
paragraph as an anchor.

Am I doing anything wrong?

Here below is my footer customization:

<xsl:param name="lastpage">
<xsl:value-of select="ancestor-or-self::article/articleinfo/biblioid"/><xsl:text>_theEnd</xsl:text></xsl:param>

<fo:block>
    <xsl:choose>
    ...
    <fo:page-number/> of
    <fo:page-number-citation>
         <xsl:attribute name="ref-id"><xsl:value-of
select="$lastpage"/></xsl:attribute>
    </fo:page-number-citation>
    ...
   </xsl:choose>
</fo:block>