diff --git a/externs/polymer-externs.js b/externs/polymer-externs.js
index 0c7b8ea458..474e0e5bde 100644
--- a/externs/polymer-externs.js
+++ b/externs/polymer-externs.js
@@ -135,6 +135,12 @@ Polymer.legacyOptimizations;
 /** @type {boolean} */
 Polymer.syncInitialRender;
 
+/** @type {boolean} */
+Polymer.legacyUndefined;
+
+/** @type {boolean} */
+Polymer.legacyNoBatch;
+
 // nb. This is explicitly 'var', as Closure Compiler checks that this is the case.
 /**
  * @constructor