Custom appendix titles... what went wrong?

I am trying to have custom Appendix Titles, just as in

<http://www.dpawson.co.uk/docbook/styling/custom.html#d2212e1235>,  i.e.

<xsl:param name="local.l10n.xml" select="document('')"/>
<l:i18n xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0">
  <l:l10n language="en">
    <l:context name="title-numbered">
      <l:template name="appendix" text="Appendix %n: %t"/>
    </l:context>
  </l:l10n>
</l:i18n>

only difference: I am using Italian.

and I confess I am feeling very stupid, because my results sum up to
nothing, and I still get an appendix title of the kind:

     A. Title

(BTW I have seen that my standard it.xml already has the chunk of code above).

Now, I could work directly on the title generating template, but I
liked the KISS way here above.

Is there something I am missing to have it work?

P.S. I am using XSL1.701.