diff --git a/lib/6to5/patch.js b/lib/6to5/patch.js
index 804c477aeb..84a518ab16 100644
--- a/lib/6to5/patch.js
+++ b/lib/6to5/patch.js
@@ -22,5 +22,7 @@ def("ImportBatchSpecifier")
   .build("name")
   .field("name", def("Identifier"));
 
+types.finalize();
+
 var estraverse = require("estraverse");
 _.extend(estraverse.VisitorKeys, t.VISITOR_KEYS);