ruby-on-rails-3 - Remember Me option with devise rails3

Question

I have used devise 2.2.4, On login page remember_me option is not working. It is also not throwing any error, neither it is saving anything in remember_at field in user table.

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :token_authenticatable, :confirmable,
  # :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,:token_authenticatable,:recoverable,      :rememberable, :trackable, :validatable#,:authentication_keys => [:login]

  # Setup accessible (or protected) attributes for your model
  attr_accessible :email, :password, :password_confirmation, :remember_me, :username, :dealer_detail_id
  validates :username, :password, :password_confirmation, :presence => true
  validates_uniqueness_of :username #, :if => :email_changed?

end