Antenna House XSL-FO Extensions not working?

Question

Any attempt to use Antenna House's xsl-fo extensions by pointing to their namespace (which gives a "page not found" btw) results in an error:

The element 'root' in namespace 'http://www.w3.org/1999/XSL/Format' has invalid child element 'document-info' in namespace 'http://www.antennahouse.com/names/XSL/Extensions'. List of possible elements expected: 'layout-master-set' in namespace 'http://www.w3.org/1999/XSL/Format'.

It appears that there's some type of namespace referencing issue where the elements in the xsl-fo namespace don't recognize that the extension elements are valid child elements?

Code looks like such:

<xsl:stylesheet version='1.0'
     xmlns:xsl='http://www.w3.org/1999/XSL/Transform'
     xmlns:axf='http://www.antennahouse.com/names/XSL/Extensions'&gt;
    <xsl:template match='/root'>
        <fo:root xmlns:fo='http://www.w3.org/1999/XSL/Format' xmlns:axf='http://www.antennahouse.com/names/XSL/Extensions'&gt;
            <axf:document-info name='title' value='value' />
        </fo:root>
    </xsl:template>
</xsl:stylesheet>

Funny that they have an example listed on their website that looks exactly the same here: http://www.antennahouse.com/xslfo/axf4-extension.htm#axf.document-info

Unfortunately it doesn't seem to be working with v4.3 of their xsl formatter.