[exim] no return-path:

procmail transport seems not to be inserting Return-Path:

ubuntu 16.04 (this was just upgraded. worked before upgrade)
Exim version 4.86_2 #2 built 05-Apr-2016 12:21:41

extracts from /var/lib/exim4/config.autogenerated

procmail router

    procmail:
      debug_print = "R: procmail for $local_part@$domain"
      driver = accept
      domains = +local_domains
      check_local_user
      transport = procmail_pipe
      require_files = ${local_part}:\
              ${if exists{/etc/procmailrc}\
            {/etc/procmailrc}{${home}/.procmailrc}}:\
              +/usr/bin/procmail
      no_verify
      no_expn

procmail transport

    procmail_pipe:
      debug_print = "T: procmail_pipe for $local_part@$domain"
      driver = pipe
      path = "/bin:/usr/bin:/usr/local/bin"
      command = "/usr/bin/procmail"
      return_path_add
      delivery_date_add
      envelope_to_add

no other occurances of procmail in file

procmail is being invoked, i can see it in ~/mail/mail.log generated
from

    MAILDIR=$HOME/mail
    DEFAULT=/var/mail/randy
    LOGFILE=$MAILDIR/mail.log

clues appreciated

randy