How does connect privilege works?

Hello,

I am trying to setup a cluster for trac databases and want to isolate each db,
by assigning a specific user to a DB.

I followed the documentation but as shown in the following example, limiting
access by connect does not seem to be working.

What am I missing?

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shridhar(at)bheem ~$ createuser testuser1
Shall the new role be a superuser? (y/n) n
Shall the new role be allowed to create databases? (y/n) y
Shall the new role be allowed to create more new roles? (y/n) y

shridhar(at)bheem ~$ createdb -O testuser1 testdb1

shridhar(at)bheem ~$ createdb testdb2

shridhar(at)bheem ~$ psql testdb2
psql (9.1.4)
Type "help" for help.

testdb2=# revoke connect ON database testdb2 FROM testuser1;
REVOKE
testdb2=# \q
shridhar(at)bheem ~$ psql -U testuser1 testdb2
psql (9.1.4)
Type "help" for help.

testdb2=> \q

shridhar(at)bheem ~$ psql test
psql (9.1.4)
Type "help" for help.

test=# select version();
version
---------------------------------------------------------------------------------------------------------
PostgreSQL 9.1.4 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.7.0
20120505 (prerelease), 64-bit
(1 row)

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Regards
Shridhar