Problem with encoding (lower() doesn't work)

Steps :
export LANG=ru_RU.KOI8-r (locale was set properly)
initdb
createdb -E WIN tst
psql tst < tsearch2.sql
psql tst :
SET client_encoding to KOI8;
create table tst (name text, v tsvector);
insert ..
update tst set v = to_tsvector(lower(nm));

and i've got capitalized russian text in v (vectors) :(

the select * from lower(); isnt working too

I've tried Postgres 8.1 and 8.2