recipient preferences

[Tenui]

 >>Hi all,
 >>When I created my key I chose AES256 as the encryption algorithm. When
 >>I encrypt to self (to encrypt a file on disk, for instance) I get the
 >> warning "gpg: forcing symmetric cipher AES256 (9) violates recipient
 >> privileges".
 >>
 >> The command "pref" gives me "S7 S3 S2 S1 H2 H3 Z2 Z1 [MDC]". If I use
 >> "setpref", what must I add to this string to include AES256?

 >AES256 == S9
 >AES192 == S8
 >AES    == S7
 >
 >David
 >   David Shaw  |  dshaw@jabberwocky.com  |  WWW http://www.jabberwocky.com/
 >+---------------------------------------------------------------------------+
Well, I have tried
setpref S9 S8 S7 S3 S2 S1 H2 H3 Z2 Z1 [mdc]
and I get
gpg: invalid character in preference string

I am using gnupg-win32-1.21-nr1 with GPGshell 2.65. Do we have a bug 
somewhere here or
am I missing that is obvious to a more experienced user?
Tenui