Update on 6.5

Hi,

I am using postgresql 6.5 snapshot.
I can not update.
Could anyone tell me what's wrong, please?

update ibs_br_all_total_units tr set first_name=
(select first_name from ibs_subscriber tnwhere tr.pin = tn.pin
);

"/tmp/psql.60000.13342" 4 lines, 117 characters
ERROR:  parser: syntax error at or near "tr"

Thanks.

Regards,
Chai