diff --git a/lib/operations/mongo_client_ops.js b/lib/operations/mongo_client_ops.js
index e99d547023..07abd31dca 100644
--- a/lib/operations/mongo_client_ops.js
+++ b/lib/operations/mongo_client_ops.js
@@ -555,23 +555,29 @@ function transformUrlOptions(_object) {
         object[i] = auth[i];
       }
     }
+
     if (auth.username) {
       object.auth = auth;
       object.user = auth.username;
     }
-    if (auth.db) {
-      object.dbName = auth.db;
-    }
   }
+
+  if (_object.defaultDatabase) {
+    object.dbName = _object.defaultDatabase;
+  }
+
   if (object.maxpoolsize) {
     object.poolSize = object.maxpoolsize;
   }
+
   if (object.readconcernlevel) {
     object.readConcern = { level: object.readconcernlevel };
   }
+
   if (object.wtimeoutms) {
     object.wtimeout = object.wtimeoutms;
   }
+
   return object;
 }