diff --git a/CHANGES.rst b/CHANGES.rst
index ccebd411..e9aa0c44 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -29,7 +29,7 @@ pywb 0.30.0 changelist
    - support custom cookie rewriter
    
 * wombat/client side improvements:
-   - rewrite ``frameElement`` -> ``WB_wombat_frameElement``, set to undefined for top replay frame
+   - rewrite ``frameElement`` -> ``WB_wombat_frameElement``, set to null for top replay frame
    - Allow changing of ``document.domain``
    - Rewrite ``<form action>`` and <input @value>`` in ``rewrite_elem``
  
diff --git a/pywb/static/wombat.js b/pywb/static/wombat.js
index 3a88c050..5fb4e2a4 100644
--- a/pywb/static/wombat.js
+++ b/pywb/static/wombat.js
@@ -18,7 +18,7 @@ This file is part of pywb, https://github.com/ikreymer/pywb
  */
 
 //============================================
-// Wombat JS-Rewriting Library v2.11
+// Wombat JS-Rewriting Library v2.12
 //============================================
 
 
@@ -2307,7 +2307,7 @@ var wombat_internal = function($wbwindow) {
             var res = this.frameElement;
 
             if (this.__WB_replay_top == this) {
-                return undefined;
+                return null;
             }
 
             return res;