xsl:number on attribute nodes..

  <xsl:template match="@* | *">
    <xsl:number count="@* | *"/>
  </xsl:template>
</xsl:stylesheet>

Saxon 6.5.4 gives me the following error:
Error at xsl:number on line 8 of file:test.xsl:
  Attribute nodes cannot be numbered
Transformation failed: Run-time errors were reported

Xalan 2.7 produces the following output:
<?xml version="1.0" encoding="UTF-8"?>11