redirect function

i use <redirect:write  method="text" append="true">
but it doesn't append in the end of file?

my xsl file:

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:lxslt="http://xml.apache.org/xslt"
xmlns:redirect="org.apache.xalan.xslt.extensions.Redirect"
extension-element-prefixes ="redirect">
<xsl:output method="text" version="1.0" encoding="ISO-8859-1"
indent="yes" omit-xml-declaration="yes" />

<xsl:template match="/">

<xsl:call-template   name="test_redirect">
 <xsl:with-param name="pcontenu" select="'aaaaaaaaaaaaaa'"/>
</xsl:call-template>

<xsl:call-template   name="test_redirect">
 <xsl:with-param name="pcontenu" select="'cccccccccccccccccc'"/>
</xsl:call-template>

</xsl:template>


<xsl:template   name="test_redirect">
<xsl:param name="pcontenu" select="nn"/>
<redirect:open file="essai.txt"/>
<redirect:write file="essai.txt" method="text" append="true">
<xsl:value-of select="$pcontenu"/>
<xsl:text>&#10;</xsl:text>
</redirect:write>
<redirect:close file="essai.txt"/>
</xsl:template>


but in the essai.txt i have:
cccccccccccccccccc
 i will have:
aaaaaaaaaaaaaa
cccccccccccccccccc




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