diff --git a/lib/6to5/transformation/transformers/es6-default-parameters.js b/lib/6to5/transformation/transformers/es6-default-parameters.js
index b369678daa..0d99b6db8e 100644
--- a/lib/6to5/transformation/transformers/es6-default-parameters.js
+++ b/lib/6to5/transformation/transformers/es6-default-parameters.js
@@ -11,6 +11,7 @@ exports.Function = function (node, parent, file, scope) {
   });
 
   var iife = false;
+  var def;
 
   var checkTDZ = function (ids) {
     var check = function (node, parent) {
@@ -30,7 +31,7 @@ exports.Function = function (node, parent, file, scope) {
   };
 
   for (var i = 0; i < node.defaults.length; i++) {
-    var def = node.defaults[i];
+    def = node.defaults[i];
     if (!def) continue;
 
     var param = node.params[i];