index on int8 in PG 6.4.2

Hello,

I got a table createtd with command:
create table test (t int8);

When I try:
create index i_test on test(t);
I get error:
ERROR:  Can't find a default operator class for type 20.

How can I define a default operator for int8???
When I am doing select * from test where t > 4, etc.
it works. 

Anyone have any idea how to define a index ont int8 field?

Mirek

--
Mirek Budzanowski; P.O. box 1739; 51-161 Wroclaw 8; Poland
Tel. +48 602 306674     http://www.tcs.uni.wroc.pl/~mirekb