NT and aborted transaction

Hi all,
still experimenting NT:

kalman=# begin;
BEGIN
kalman=# select * from a;
ERROR: relation "a" does not exist
kalman=# begin;
BEGIN
kalman=# select * from test;
ERROR: current transaction is aborted, commands ignored until end of transaction block

I think the second begin shall fail instead of open an already invalid transaction.

Regards
Gaetano Mendola