Unknown column 'plugin' when adding User

[Rajnesh]

I have just installed the plugin auth_pam.so form mysql authentication

However, I am getting the following error when creating a user to
authenticated against ldap:
--------------------------------------------------------------------------------------------------------------
mysql> CREATE USER 'rsiwal'@'localhost' IDENTIFIED WITH auth_pam;
ERROR 1054 (42S22): Unknown column 'plugin' in 'mysql.user'
--------------------------------------------------------------------------------------------------------------
MySQl version: 5.5.25

Please suggest.