DOCBOOK: javahelp stylesheet problems

Hello,
when trying to apply the javahelp stylesheet with saxon to the test file
docbook40.xml, I get the following error:

saxon -o docbook40.jh docbook40.xml
/usr/local/lib/sgml/stylesheet/xsl/docbook/javahelp/docbook.xsl
Failed to compile style sheet
At xsl:with-param on line 98 of
file:/usr/local/lib/sgml/stylesheet/xsl/docbook/javahelp/docbook.xsl:
Variable object has not been declared

Does anybody have an idea what is going wrong?
Thanks,
Patrick