How to use index in case insensitive substing search

How to force postgres to use index for the following query (I can change the
query to equivalent if required)

select nimi from klient where lower(nimi) like 'test%'

Currently it does NOT use index:

create index nimib2 on firma1.klient(lower(nimi) bpchar_pattern_ops);
explain analyze select nimi from firma1.klient where lower(nimi) like
'mokter%'

"Seq Scan on klient  (cost=0.00..9.79 rows=1 width=74) (actual
time=0.740..0.761 rows=1 loops=1)"
"  Filter: (lower((nimi)::text) ~~ 'mokter%'::text)"
"Total runtime: 0.877 ms"

Postgres 8.1 UTF8 encoding in Windows XP

Note.

Query

explain analyze select nimi from firma1.klient where nimi like 'Mokter%'

for same data uses index:

"Index Scan using nimib on klient  (cost=0.00..5.80 rows=1 width=74) (actual
time=9.402..9.427 rows=1 loops=1)"
"  Index Cond: ((nimi ~>=~ 'Mokter'::bpchar) AND (nimi ~<~
'Moktes'::bpchar))"
"  Filter: (nimi ~~ 'Mokter%'::text)"
"Total runtime: 9.615 ms"

Andrus.