Reset footnote numbering for each chunk

Dear All,

my HTML output consists of (manually) chunked chapters and sections.
However, my footnotes are still numbered from the beginning. 

I've located the following template in the html/footnote.xsl:

<xsl:template match="footnote" mode="footnote.number">

which implements quite basic counting (simplified here for better
understanding):

<xsl:variable name="fnum" select="count(preceding::footnote) + 1"/> 

Is there a simple way to get actual chunk element inside this template and
modify the above code to select just 'preceding::footnote' up to that chunk
element?

Thanks,

Jan