Problem with faked-system-time option

[Amano Corunga]

In doc\gpg.man of my gnupg 1.4.11 I found

--faked-system-time epoch
    This  option is only useful for testing; it sets the system time
    back or forth to epoch which is the number  of  seconds  elapsed
    since the year 1970.  Alternatively epoch may be given as a full
    ISO time string (e.g. "20070924T154812").

a real goody, as nobody has to know at what (night-)time I create keys
or work off (and sign) my mail.  But I can't get it working:

| Microsoft Windows [Version 6.1.7600]
| Copyright (c) 2009 Microsoft Corporation.  All rights reserved.
| 
| e:\portapps\GnuPG>gpg --homedir .\data
|                       --faked-system-time 20110501T120000
|                       --gen-key
| gpg: Invalid option "--faked-system-time"

Transferring a number instead of the time string and putting it in
quotation marks doesn't help either.

Any hint appreciated.

Amano