title: Uncaught MongoError: unrecognized field 'allowDiskUsage'
body: <p>I installed 2.5.5 so that I can try the new "$out" operator to create new collections with aggregation results. My node adapter is mongodb@1.3.23. I don't have "allowDiskUsage" in my code, but I get this error:</p>
  
  <pre><code>Uncaught MongoError: unrecognized field 'allowDiskUsage'
  </code></pre>
  
  <p>What do I need to do to update my project to run 2.5.5?</p>