6.5.2 create index bug?

Can anybody verify whether this is a bug in 6.5.2?  I compiled 6.5.2
from sources, everything seemed OK.

I created a table:
    CREATE TABLE TESTTBL (A int4);

Then tried to create a unique index:
    CREATE UNIQUE INDEX TESTTBL0 ON TESTTBL (A);

The above failed, but the following succeeded:
    CREATE UNIQUE INDEX TESTTBL_0 ON TESTTBL (A);

Thank you.