diff --git a/lib/do.js b/lib/do.js
index d7f250a..0c0af0e 100644
--- a/lib/do.js
+++ b/lib/do.js
@@ -143,7 +143,10 @@ exports.cont = function (fn) {
 // the specified names to continuable style and returns the new library.
 exports.convert = function (lib, names) {
   var newlib = {};
-  names.forEach(function (key) {
+  Object.keys(lib).forEach(function (key) {
+    if (names.indexOf(key) < 0) {
+      return newlib[key] = lib[key];
+    }
     newlib[key] = function () {
       var args = Array.prototype.slice.call(arguments);
       return function (callback, errback) {