HTML chunks not written if template for chapter inserted intocustomization layer

I was inserting the template for d:chapter (from html/component.xsl) into  
my customization layer when chunking suddenly didn't work anymore. I  
managed to create the following customization layer to reproduce the  
problem:

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"  
version="1.0"
xmlns:d="http://docbook.org/ns/docbook" exclude-result-prefixes="d">
   <xsl:import href="docbook-xsl-ns-1.74.0/html/chunkfast.xsl"/>
   <xsl:param name="chunk.section.depth" select="0"/>
   <xsl:template match="d:chapter"/>
</xsl:stylesheet>

If you remove either the parameter chunk.section.depth or the template for  
d:chapter chunks are written. Is this a bug? If not can anyone tell me how  
I can customize the chapter if I can't insert the template for d:chapter?

Before someone asks: You can also copy&paste the original template from  
html/component.xsl - same problem.

Boris