diff --git a/lib/api/2011-02-01/configuration.js b/lib/api/2011-02-01/configuration.js
index <HASH>..<HASH> 100644
--- a/lib/api/2011-02-01/configuration.js
+++ b/lib/api/2011-02-01/configuration.js
@@ -433,7 +433,12 @@ handlers.DescribeIndexFields = function(context, request, response, config) {
           throw new errors.MalformedInputError('Key ' + match[1] + ' may not have a leading \'' + match[1].charAt(0) + '\'');
         return true;
       });
-  var fieldNames = keys.sort().map(function(key) {
+  var appeared = {};
+  var fieldNames = keys.sort().filter(function(key) {
+        if (key in appeared) return false;
+        appeared[key] = true;
+        return true;
+      }).map(function(key) {
         return request.query[key];
       });
   var fields = fieldNames.length ?
Don't output duplicated index fields