[Exim] syntax_errors_to and filter files

My configuration defines user forward files as follows:

    userforward:
      driver = forwardfile
      file_transport = address_file
      pipe_transport = address_pipe
      reply_transport = address_reply
      suffix = -*
      suffix_optional
      no_verify
      check_ancestor
      check_local_user
      file = .forward
      syntax_errors_to = postmaster
      filter

However, when a mangled ~/.forward is encountered, the message is deferred:

  LOG: 0 MAIN
    == ephraim@??? D=userforward defer (-11): error in filter file:
       unknown filtering command "lgfile" near line 10 of filter file

but _no_ message is sent to 'postmaster' informing him about the syntax error
in the user's forward file.

What am I doing wrong?
___________________________________________________________________________
Ephraim Silverberg, CSE System Group,        Phone number:    972-2-6585521
Hebrew University, Jerusalem, Israel.        Fax number:      972-2-6585439
WWW: http://www.cs.huji.ac.il/~ephraim       E-mail: ephraim@???