shmk on "password_reset hook missing argument 2"

I'm trying to attach a function to the password_reset hook:

function my_password_reset($user, $new_password){
    /* actions */
}
add_action('password_reset', 'my_password_reset');

But it returns me the error that the second parameter, the plain password, is not passed to my function.

Warning: Missing argument 2 for my_password_reset()

I can't understand what is wrong with my function, anyone could help me?