Mutt: folder-hook + set index_format= doesn't work?

[Chris Halls]

Hi folks,

I wanted to check that I'm not doing something silly before I file a bug.

I wanted to change the message header display in mutt on a per-folder
basis.  From the documentation it seems that the way to do that is with a
folder-hook line in my .muttrc, giving the new set index_format command
for the folder.  For example:

folder-hook mbox set index_format="%4C %Z %s"   

But when I load the folder, an error message appears in the status line,
'%Z: unknown variable'.  Strangely enough, the non folder-hook variant
works:

set index_format="%4C %Z %s"                    # Works OK

Are there special rules for the folder-hook line, or should I be able to
do this?  I'm using mutt 1.3.20-1 (Woody/Sid)

Thanks,
Chris Halls