setting up listener password in Oracle 10g

hi,
I have problem setting up the password for Oracle 10g listener. After successfully setting up the listener password, I was still able to stop the listener without having to provide a password. I did verify that the PASSWORDS_LISTENER clause was added in listener.ora.

The steps I ran are listed below. Works fine in 9i but not in 10g. Looked up in the documentation but could not find anything that has changed in 10g. Has anyone experienced this or know what the problem is?

LSNRCTL> change_password
Old password:
New password:
Reenter new password:
Connecting to
(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=devhpv)(PORT=1521))) Password changed for LISTENER
The command completed successfully
LSNRCTL> save_config
Connecting to
(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=devhpv)(PORT=1521))) Saved LISTENER configuration parameters. Listener Parameter File
/app/oracle/product/10.2.0/network/admin/listener.ora Old Parameter File
/app/oracle/product/10.2.0/network/admin/listener.bak The command completed successfully

LSNRCTL> exit

$> lsnrctl stop

LSNRCTL for Solaris: Version 10.2.0.2.0 - Production on 20-JUL-2006 9:18:10

Copyright (c) 1991, 2005, Oracle. All rights reserved.

Connecting to
(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=devhpv)(PORT=1521))) The command completed successfully Received on Thu Jul 20 2006 - 11:48:23 CDT