comment() node test

I'm trying to display the value of the previous sibling if it is a comment.
What's wrong with my XPath expression?  It won't display anything.

<xsl:for-each select="element">
  <xsl:value-of select="preceding-sibling::node()[1][self::comment()]"/>
</xsl:for-each>


I've confirmed that the parser I'm using passes comments to the XSLT
processor (Instant Saxon), as the comment() node test works in other cases,
such as the following:

<xsl:for-each select="comment()">
  <xsl:value-of select="."/>
</xsl:for-each>

Thanks,

Evan Lenz
elenz@xxxxxxxxxxx


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