postgresql unicode lower/upper problem

I am not able to get work lower and upper functions on postgresql
v8.0.1 and 8.1b(current cvs copy). I use Debian SID i686 GNU/Linux.
Locale: ru_RU.KOI8-R

createdb -E UNICODE test
psql test

test=> SET client_encoding TO KOI8;
SET
test=> SELECT t FROM t1;
   t
--------
 пРиВЕТ
 tEsT
(2 rows)

test=> SELECT upper(t) FROM t1;
 upper
--------
 пРиВЕТ
 TEST

test=> SELECT lower(t) FROM t1;
 lower
--------
 пРиВЕТ
 test
(2 rows)

How you can see it work perfect with latin and does not do any
lower/upper with koi8.
what I do wrong?