CUPS: Can't set option for halftoning algorithm after upgrade from Debian squeeze to lenny

CUPS: Can't set option for halftoning algorithm after upgrade from Debian squeeze to lenny

After upgrading my main Debian box from squeeze to lenny recently, I couldn't set the option for my printer's halftoning algorithm any more. It appears that the upgrade of cups that happened during the dist upgrade has dumbed down my printer's ppd file.
How do I get this option back?