diff --git a/lib/widget.js b/lib/widget.js
index e5339e6..4b93ae9 100644
--- a/lib/widget.js
+++ b/lib/widget.js
@@ -4853,6 +4853,8 @@ Button.prototype.press = function() {
  */
 
 function ProgressBar(options) {
+  var self = this;
+
   if (!(this instanceof Node)) {
     return new ProgressBar(options);
   }