ruby 1.9.2 restful_authentication plugin unknown encoding name: mule-utf-8 issue

The issue
=> Booting WEBrick
=> Rails 2.3.10 application starting on http://0.0.0.0:3000
C:/Users/project/vendor/plugins/restful-authentication/lib/authentication/by_cookie_token.rb:1: unknown encoding name: mule-utf-8 (ArgumentError)
from :29:in `require'
from :29:in `require'


To fix this
replace line no 1 (# -*- coding: mule-utf-8 -*-) of /vendor/plugins/restful-authentication/lib/authentication/by_cookie_token.rb
with # -*- coding: utf-8 -*-