Setting gnus-list-identifiers on a per-group basis

[Paul Moore <gustav@morpheus.demon.co.uk>]

I have

    (setq gnus-list-identifiers '("\\[[^]]*\\]" "(Fwd)" "AW:"))

in my .gnus.el, in order to strip [list-id] junk from the start of
subject lines. However, I have a newsgroup (rec.games.roguelike.angband)
where [xx] is used for a useful subject convention, so I'd like to set
gnus-list-identifiers to just '("(Fwd)" "AW:") in that group.

I tried G c to customize the group parameters, and set

    Variables:
    Set variables local to the group you are entering. *
    [INS] [DEL] Variable: gnus-list-identifiers
                Value: '("(Fwd)" "AW:")

When I go into the summary buffer and do C-H v, I see that
gnus-list-identifiers has the value I specified as a buffer-local
value, but the summary reflects the global value.

Should I be setting this differently? Is it a timing issue (the
group-specific value not being set until after the summary has been
generated)?

Thanks,
Paul Moore.