title: Rails3: uninitialized constant Mime::MOBILE
body: <p>I use <a href="https://github.com/brendanlim/mobile-fu" rel="nofollow">mobile-fu</a> to automatically detect mobile devices that access My Rails application.</p>
  
  <p>When My rails version is 3.2.8</p>
  
  <p>my config/initializers/mime_types.rb</p>
  
  <pre><code>Mime::Type.register_alias "text/html", :mobile
  </code></pre>
  
  <p>My WelcomeController </p>
  
  <pre><code>def index
    respond_to do |format|
      format.mobile 
      format.html
    end
  end
  </code></pre>
  
  <p>When I visit welcome/indx , I got this error:</p>
  
  <pre><code>uninitialized constant Mime::MOBILE
  </code></pre>
  
  <p>When I change rails to 3.2.3 , It works fine. </p>
  
  <p>Is anybody know that?</p>
  
  <p>Thanks!</p>