Charsets v grep

[rclayton@monmouth.edu (R. Clayton)]

I'm running this

  $ bash --version
  GNU bash, version 4.3.42(1)-release (i586-pc-linux-gnu)
  Copyright (C) 2013 Free Software Foundation, Inc.
  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

  This is free software; you are free to change and redistribute it.
  There is NO WARRANTY, to the extent permitted by law.

  $

on this

  $ lsb_release -a
  No LSB modules are available.
  Distributor ID:   Debian
  Description:      Debian GNU/Linux testing-updates (sid)
  Release:          testing-updates
  Codename:         sid

  $

and I've been getting a lot of this lately:

  $ grep ^Subject: cbtm 
  Binary file cbtm matches

  $

whereas before (a month or so ago) I used to get actual matches on std-out.
It's easy enough to work around like so

  $ sed -n -e '/^Subject:/p' < cbtm 
  Subject: Re: PTFACULTY: FTFACULTY: When saying "Nous sommes Paris" is not
  Subject: FTFACULTY: When saying "Nous sommes Paris" is not enough
  Subject: Lowered Reserve Prices

  $

but I'd like to grep working like it used to.  What is the way for me to get
grep back?  Some other points that may be useful:

  $ file cbtm 
  cbtm: ISO-8859 text, with very long lines

  $ ba env | grep -i utf
  LANG=en_US.UTF-8
  XTERM_LOCALE=en_US.UTF-8

  $