exim + courier-imap catch-all?

["Alan J. Cooper" <alan@mail.avontoun.co.uk>]

I'm running debian unstable on my server trying to set up a mail server 
with Exim (3.36)  running as MTA and also running courier-imap.

With just exim installed, I use search_type = lsearch* with a *: 
catchall entry in my alias file so that any misaddressed email goes to 
the catchall account. This works fine and the mail is delivered 
correctly to /var/mail/$username files.

However, to use courier, I modified exim.conf local_delivery to look 
like
local_delivery:
  driver = appendfile
  group = mail
  mode = 0660
  mode_fail_narrower = false
  envelope_to_add = true
  return_path_add = true

  directory=${home}/Maildir
  maildir_format = true
  prefix = ""

And now everything including correctly addressed email goes to the 
catchall. If I change search_type = lsearch* to search_type = lsearch 
then all mail goes to the correct users but misaddressed email is 
bounced.

Is there anyway to have a catchall with delivery compatible with 
courier-imap?