diff --git a/lib/6to5/transformation/transformers/playground/method-binding.js b/lib/6to5/transformation/transformers/playground/method-binding.js
index 3835d04543..de8277740e 100644
--- a/lib/6to5/transformation/transformers/playground/method-binding.js
+++ b/lib/6to5/transformation/transformers/playground/method-binding.js
@@ -26,7 +26,7 @@ exports.BindMemberExpression = function (node, parent, scope) {
   }
 };
 
-exports.BindFunctionExpression = function (node, parent, scope, file) {
+exports.BindFunctionExpression = function (node, parent, scope) {
   var buildCall = function (args) {
     var param = scope.generateUidIdentifier("val");
     return t.functionExpression(null, [param], t.blockStatement([