[exim] case lost in local part of address

Hallo all,

I am post here this message because looks like exim.org does not have
bugzilla (why?)...

We are using the custom mail drop (virt_mail) program which delivers
mails through ODBC to the Virtuoso RDBMS.
Here is a piece of exim4.conf file:

#DIRECTORS
...

to_db:
debug_print = "R: to_db for $local_part@$domain"
driver = accept
caseful_local_part
require_files = /etc/odbc_mail.ini
retry_use_local_part
transport = odbc

...

#TRANSPORT

...

odbc:
  debug_print = "R: odbc deliver $local_part@$domain"
  driver = pipe
  command = /usr/local/bin/virt_mail \
            -c /etc/odbc_mail.ini \
            -s "${if def:return_path{$return_path}{MAILER-DAEMON}}" \
            -l "$local_part" -h "$domain" -D
  delivery_date_add
  message_prefix =
  message_suffix =
  return_fail_output
  return_path_add
  temp_errors = 73 : 74 : 75
  user = rus

But the /usr/local/bin/virt_mail receive the mail with caseless local
part, even caseful_local_part is set...
Did I do something wrong? Or it is a bug?

exim version is 4.34-9 (backported for Debian Woody)

Thanks for advance.

Ruslan Abdulkhalikov