brew install mysql, error when trying to stop the server

After:

brew install mysql
mysql_install_db

and I try to stop the MySQL server:

$ mysql.server stop
Shutting down MySQL
.. ERROR! Manager of pid-file quit without updating file.

How can I fix the above error? Thanks!

Info:

$ mysql -v
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.1.51 Source distribution