diff --git a/lib/6to5/transformation/transformers/spec/block-scoped-functions.js b/lib/6to5/transformation/transformers/spec/block-scoped-functions.js
index 1f7f4c7ef0..9aeffc454f 100644
--- a/lib/6to5/transformation/transformers/spec/block-scoped-functions.js
+++ b/lib/6to5/transformation/transformers/spec/block-scoped-functions.js
@@ -3,13 +3,13 @@
 var t = require("../../../types");
 
 exports.BlockStatement = function (node, parent) {
-  if (t.isFunction(parent) || t.isExportDeclaration(parent)) {
+  if ((t.isFunction(parent) && parent.body === node) || t.isExportDeclaration(parent)) {
     return;
   }
 
   for (var i = 0; i < node.body.length; i++) {
     var func = node.body[i];
-    if (!t.isFunctionDeclaration(i)) continue;
+    if (!t.isFunctionDeclaration(func)) continue;
 
     var declar = t.variableDeclaration("let", [
       t.variableDeclarator(func.id, t.toExpression(func))
@@ -21,6 +21,6 @@ exports.BlockStatement = function (node, parent) {
     // todo: name this
     func.id = null;
 
-    func.body[i] = declar;
+    node.body[i] = declar;
   }
 };