DOCBOOK-APPS: i can't seem to chunk more than level 2

["Robert P. J. Day" <rpjday at mindspring dot com>]

  i have a docbook file that, for the first time, is using
three levels of sectioning, but even when i set the chunking
level to 3, it refuses to go beyond two.

  here's my chunk.xsl file:

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
                xmlns:fo="http://www.w3.org/1999/XSL/Format";
                version='1.0'>

<!-- Turn on chunking. -->
<xsl:param name="chunk.section.depth" select="'3'"/>

</xsl:stylesheet>

  i reduced it to 1, and that formatted accordingly.  increasing
the value to 2 worked as well, but going to 3 didn't change anything.
is there some associated feature or value i need to adjust as well?

rday