diff --git a/lib/task.js b/lib/task.js
index 7e69864..4ece128 100644
--- a/lib/task.js
+++ b/lib/task.js
@@ -101,7 +101,7 @@ Promise.prototype = {
         return this.then(callback);
     },
     addErrback: function(errback) {
-        return this.then(function(){}, errback);
+        return this.then(function(arg){ return arg }, errback);
     },
     addBoth: function(callback) {
         return this.then(callback, callback);