diff --git a/lib/6to5/transformation/transformers/optional-block-scoping-tdz.js b/lib/6to5/transformation/transformers/optional-block-scoping-tdz.js
index 22a9474197..972cca4567 100644
--- a/lib/6to5/transformation/transformers/optional-block-scoping-tdz.js
+++ b/lib/6to5/transformation/transformers/optional-block-scoping-tdz.js
@@ -3,7 +3,7 @@ var t        = require("../../types");
 
 exports.optional = true;
 
-exports.Loop
+exports.Loop =
 exports.Program =
 exports.BlockStatement = function (node, parent, scope, context, file) {
   var letRefs = node._letReferences;