dictionary order bug

The dictionary order option does not sort in dictionary order:

$ echo 'aB\nab\nAb' | sort -d -f
ab
aB
Ab

It should be:

Ab
aB
ab

Certainly Merriam-Webster lists Ab before ab.

$ sort --version
sort (textutils) 2.0.21
Written by Mike Haertel and Paul Eggert.

Copyright (C) 2002 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

-- 
  John Mocenigo                          E-Mail: [email protected]
  Research @ AT&T Labs                   Voice: 1-973-360-8639
  180 Park Av / Bldg 103 / Rm D-225      Fax: 1-973-360-8055
  Florham Park, NJ 07932-0971