[Exim] V4 mailman -- ${lc:$local_part} failure

hi

I am testing V4.05 based on running convert4r4 on my exim v3.36 config
file. Most stuff seems to work fine, including all my ldap lookups
etc. But the Mailman stuff errors out


host: {224} /usr/local/exim4/bin/exim -bt wessexlist@???
wessexlist@??? cannot be resolved at this time:
failed to expand "/usr/local/mailman/lists/${lc" for require_files:
"${lc" is not a known operator (or a } is missing in a variable
reference)
host: {225}


here is an appropriate line in the config file

list_director:
driver = accept
domains = lists.shire.net:frogmorton.shire.net
require_files = MAILMAN_HOME/lists/${lc:$local_part}/config.db
retry_use_local_part
transport = list_transport


This looks fine to me according to what I read in the V4 docs for
variable expansion and lower casing...

Any help on spotting the problem is gladly accepted.

Thanks
Chad