DOCBOOK-APPS: Chunked HTML and TOCs

Using:
- DocBook XML 4.1.2
- DocBook XSL 1.51.1
- xsltproc (libxml2 2.4.22, libxslt 1.0.18)

In generating chunked HTML output I want to have TOCs up to the second 
level and set the following in my XSL customization layer:

<xsl:param name="generate.section.toc.level" select="2"/>

But I get only a complete TOC for the first section and no TOC at the
deeper levels.

Any hints?

Michael
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