My xsl-fo stylesheet don't add my page number prefix as expected

I'm trying to change the way the index page works by adding to it a number present in the xml. so in theory this is supposed to be made out of the box, but for some reason the output doesn't have my page-number prefix.

for example, if the node somethingElse has the value, 57 and is on the page 13 I want to have 57.13 displayed on the index but only 13 gets displayed.

I tried to change value-of/inline to a block conataining only a word test, but even that doesn't seem to work. So I can only assume that I'm not using index-page-number-prefix correctly...

What am I doing wrong ?

<fo:block>
    <fo:inline font-weight="normal">
    <fo:leader leader-pattern="dots"/>
        <fo:index-page-citation-list>
            <fo:index-key-reference ref-index-key="{.};{../title};;" font-weight="bold">
                <fo:index-page-number-prefix>
                    <fo:inline>
                    <xsl:value-of select="ancestor::something/SomethigElse"/>.
                    </fo:inline>
                </fo:index-page-number-prefix>
            </fo:index-key-reference>
        </fo:index-page-citation-list>
    </fo:inline>
</fo:block>

Solution

fo:index-page-number-prefix is ignored by RenderX. See http://www.renderx.com/reference.html#XSL11_Support or, more specifically, http://www.renderx.com/reference.html#XSL11_Indexes.