title: MongoDB Text Index Error: language override not supported
body: <p>I am using version 2.6.1. I am trying to create a text index and I'm getting error:</p>
  
  <pre><code>{
      "connectionId" : 4932,
      "err" : "language override unsupported: en-US",
      "code" : 17262,
      "n" : 0,
      "ok" : 1
  }
  </code></pre>
  
  <p>The documents being searched have a "language" field that has a value of "en-US", but it is not used to override the language in a text search. I tried to create the text index to specify a field that doesn't exist ("lang"); however, I get the same error.
  I was able to create the index just fine on version 2.6.0. Is there a way to create the text index and ignore the language_override field?</p>
  
  <p>Here is the working command I used on 2.6.0 (doesn't work on 2.6.1):</p>
  
  <pre><code>db.collection.ensureIndex({ title: "text" }, { name: "TextIndex" })
  </code></pre>
  
  <p>Here is the command I tried on 2.6.1 to specify another language_override field that does not exist:</p>
  
  <pre><code>db.collection.ensureIndex({ title: "text" }, { name: "TextIndex" }, { language_override: "lang" })
  </code></pre>
  
  <p>Thanks in advance!</p>