Rails - Sep 2005 - All caps in controller names

Are controller names allowed to have all caps, like PDFController?

I created a controller called PDFController with the generator and it croaks 
with an unknown constant PdfHelper error.  Is that not the convention?

I reported this as a bug, but now I''m not so sure because the wiki
doesn''t
recognize PDFController as a valid wiki word.

-Jeff