Functions of XSLT Version 2

 Hi, I'm trying to use the function "upper-case" in XSLT version 2.0 but Oracle gives me back LPX-00607: invalid reference.

Here is the example:

declare
  origin  sys.xmltype;
  destination sys.xmltype;
  transformation sys.xmltype;
 
  v_out varchar2(500);
 
begin
  origin := xmltype('<?xml version="1.0" encoding="UTF-8"?>
                     <pessoas>
                           <pessoa>
                                <nome>Flavio</nome>
                                <Idade>34</Idade>
                           </pessoa>
                     </pessoas>');

  transformation := xmltype('<?xml version="1.0" encoding="UTF-8"?>
                      <xsl:stylesheet version="2.0"
                                      xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                                      xmlns:fn="http://www.w3.org/2005/xpath-functions"
                                      xmlns:xs="http://www.w3.org/2001/XMLSchema" >
                        <xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
                      <xsl:template match="/pessoas">
                        <people>