<&#220;belkeit/> - ASCIIfied element name (LibXSLT/xs

Any valid Unicode character is allowed in an element name,
which is great.

<Urmel>
  <Vorspeise>S|_kirschen mit Kdseso_e</Vorspeise>
  <\belkeit/>
</Urmel>

<xsl:transform version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output encoding="us-ascii"/><!-- Alles ASCII ! -->
  <xsl:template match="@*|node()">
    <xsl:copy>
      <xsl:apply-templates select="@*|node()"/>
    </xsl:copy>
  </xsl:template>
</xsl:transform>

Error at xsl:copy on line 5 of file:/home/mludwig/Werkstatt/xsl/ascii.xsl:
  Invalid character in output name (\belkeit)
Transformation failed: Run-time errors were reported

<?xml version="1.0" encoding="us-ascii"?>
<Urmel>
        <Vorspeise>S&#252;&#223;kirschen mit K&#228;seso&#223;e</Vorspeise>
        <&#220;belkeit/>
</Urmel>

So is LibXSLT preferable in this respect? Or would I be justified
reporting this as a bug?