lpadmin custom option setting does not work, CUPS 1.4.3

[Mintze van der Velde]

Hi, I use the following PPD snippet:

*OpenUI *Mailbox/Boite aux lettres (0-99): PickOne
*FoomaticRIPOption Mailbox: string CmdLine I
*FoomaticRIPOptionMaxLength Mailbox: 2
*FoomaticRIPOptionAllowedChars Mailbox: "0-9"
*OrderDependency: 20 AnySetup *Mailbox
*FoomaticRIPOptionPrototype Mailbox: " -BB=%s"
*DefaultMailbox: None
*Mailbox None/Aucun: "%% FoomaticRIPOptionSetting: Mailbox=None"
*FoomaticRIPOptionSetting Mailbox=None: ""
*CloseUI: *Mailbox
*CustomMailbox True: "%% FoomaticRIPOptionSetting: Mailbox=\1"
*ParamCustomMailbox Mailbox: 1 string 0 2

When sending lp -dfoo -o Mailbox=Custom.33 fileName
this works, and sets the Maibox option -BB=33, which is further processed.
When, however, using:
lpadmin -pfoo -o Mailbox=Custom.33
the PPD file's DefaultMailbox is not updated.
When using the CUPS web interface, with the same PPD and setting a custom mail box = 33, then *DefaultMailbox: Custom.33  is obtained in the PPD file.
I tested this on Fedora 13 and Ubuntu 10.04LTS, with the same result.
Question: how should I use lpadmin to obtain the change in the PPD?
I would prefere *not* to use lpoptions.
Thanks for any help,

Mintze