[Exim] Exim + courier-imap + catchall address

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?