diff --git a/lib/6to5/patch.js b/lib/6to5/patch.js
new file mode 100644
index 0000000000..d985c29b19
--- /dev/null
+++ b/lib/6to5/patch.js
@@ -0,0 +1,13 @@
+var estraverse = require("estraverse");
+var types      = require("ast-types");
+var t          = require("./types");
+var _          = require("lodash");
+
+var def = types.Type.def;
+
+def("ParenthesizedExpression")
+  .bases("Expression")
+  .build("expression")
+  .field("expression", def("Expression"));
+
+_.extend(estraverse.VisitorKeys, t.VISITOR_KEYS);