Trouble formatting PDF TOC entries

<xsl:attribute-set name="toc.line.properties">
  <xsl:attribute name="font-size">10pt</xsl:attribute>
  <xsl:attribute name="font-weight">
    <xsl:when test="self::chapter | self::preface | self::appendix">bold</xsl:when>
    <xsl:otherwise>normal</xsl:otherwise>
  </xsl:attribute>
</xsl:attribute-set>