Does SoapUI NG XQuery assertions support fn: calls?

<Results>
{
for $x in //System/Response/Genie/GenieRows/GenieRow
order by $x/@Column1, $x/@Column2, $x/@Column3, $x/@Column4, $x/@Column5, $x/@Column6
return <GenieRow>{$x/@Column1} {$x/@Column2} {fn:lower-case($x/@Column3)} {$x/@Column4} {$x/@Column5} {$x/@Column6}</GenieRow>
}
</Results>

The fn:lower-case call keeps returning "RuntimeException:Error binding this".

Thanks in advance