DOCBOOK: superscript

Hi, I've got a <superscript> problem. When I write 
10<superscript>16</superscript> the 16 won't be shifted up. The 16 becomes 
smaller but the baseline is still the same as for 10. It looks like in the 
figure at http://mclim.dnsq.org/~tim/superscript.jpg

This might not be a DocBook error, but rather a LaTeX error as the figure 
shows how it looks converted to LaTeX and PDF. I use the packages OpenJade 
1.3 and docbook-style-dsssl-1.72.

Is this a known problem?

Thanks,

Tim