glossary missing from xhtml output

Is there any obvious (or not-so-obvious) reason that my glossary is 
missing (blank) from XHTML chunked output? I see a glossary section and 
glossary page in the output, but no glosslist or glossentries. My 
<glossary> is a child of <book>.

I've tried both the 1.72.0 and 1.73.0 stylesheets, with no difference. 
FO/PDF output shows the glossary just fine.

My customization layer is here:
http://pastebin.com/me635a7

Thanks,

Brett