diff --git a/lib/6to5/transformers/destructuring.js b/lib/6to5/transformers/destructuring.js
index e434bddbd6..bdc130a0a8 100644
--- a/lib/6to5/transformers/destructuring.js
+++ b/lib/6to5/transformers/destructuring.js
@@ -85,7 +85,6 @@ exports.ForOfStatement = function (node, parent, file) {
 };
 
 exports.Function = function (node, parent, file) {
-  var block = node.body;
   var nodes = [];
 
   var hasDestructuring = false;
@@ -100,8 +99,11 @@ exports.Function = function (node, parent, file) {
   });
 
   if (!hasDestructuring) return;
+
   util.ensureBlock(node);
-  block.body = nodes.concat(block.body || []);
+
+  var block = node.body;
+  block.body = nodes.concat(block.body);
 };
 
 exports.ExpressionStatement = function (node, parent, file) {