ERROR: Conditional NOTIFY is not implemented

Why I get this ERROR?. Maybe I do not use the accurate syntax?.

postgresql 7.1.3
I use Debian GNU/Linux (woody) on Intel.

Regards,
Davi Leal

$ createdb test
CREATE DATABASE

$ psql test
test=# CREATE TABLE prod
test-# (
test(# id serial
test(# );
NOTICE: CREATE TABLE will create implicit sequence 'prod_id_seq' for SERIAL
column 'prod.id'
NOTICE: CREATE TABLE/UNIQUE will create implicit index 'prod_id_key' for
table
'prod'
CREATE
test=#
test=#
test=# CREATE RULE pr AS ON DELETE TO prod DO (NOTIFY TBL2);
CREATE
test=#
test=#
test=# INSERT INTO prod DEFAULT VALUES;
INSERT 19315 1
test=# INSERT INTO prod DEFAULT VALUES;
INSERT 19316 1
test=#
test=# SELECT * FROM prod;
id
----
1
2
(2 rows)

test=# DELETE FROM prod WHERE id=1;
ERROR: Conditional NOTIFY is not implemented
test=# \q
$