diff --git a/lib/6to5/transformation/transformers/es6-let-scoping.js b/lib/6to5/transformation/transformers/es6-let-scoping.js
index 75e17812e8..44151d58b8 100644
--- a/lib/6to5/transformation/transformers/es6-let-scoping.js
+++ b/lib/6to5/transformation/transformers/es6-let-scoping.js
@@ -376,7 +376,7 @@ LetScoping.prototype.getLetReferences = function () {
 
             // this scope has a variable with the same name so it couldn't belong
             // to our let scope
-            if (scope.hasOwn(node.name)) return;
+            if (scope.hasOwn(node.name, true)) return;
 
             closurify = true;