diff --git a/lib/once.js b/lib/once.js
index 369ee162e..a851af259 100644
--- a/lib/once.js
+++ b/lib/once.js
@@ -1,8 +1,7 @@
-module.exports = function (f) {
-    var called;
+module.exports = function (f, g) {
     return function () {
-        if (called) { return; }
-        called = true;
+        if (!f) { return; }
         f.apply(this, Array.prototype.slice.call(arguments));
+        f = g;
     };
 };