title: How to use the I18n fallback features in Rails 3
body: <p>I am getting an &quot;translation missing&quot; error message from Rails 3:</p>
  <pre><code>activerecord:
    notices:
      messages:
        success: 
          create: &quot;Something was created&quot;
      models:
        user:
          success:
            create: &quot;Thanks for registration&quot;
  
  I18n.t(&quot;activerecord.notices.models.user.success.create&quot;)
  # =&gt; &quot;Thanks for registration&quot;
  
  
  I18n.t(&quot;activerecord.notices.models.book.success.create&quot;) 
  # =&gt; &quot;translation missing: de, activerecord, notices, models, book, success, create&quot;
  </code></pre>
  <p>I don't know why the book model doesn't get the fallback massage. I have set <code>config.i18n.fallbacks = true</code>.</p>