diff --git a/packages/mongo/mongo_driver.js b/packages/mongo/mongo_driver.js
index f05424094e..9c17458fee 100644
--- a/packages/mongo/mongo_driver.js
+++ b/packages/mongo/mongo_driver.js
@@ -781,7 +781,6 @@ MongoConnection.prototype.findOne = function (collection_name, selector,
 MongoConnection.prototype._ensureIndex = function (collectionName, index,
                                                    options) {
   var self = this;
-  options = _.extend({safe: true}, options);
 
   // We expect this function to be called at startup, not from within a method,
   // so we don't interact with the write fence.