diff --git a/CHANGELOG b/CHANGELOG
index 86a1cd6..c6caabe 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Ensure Ajax.Response#getHeader returns null for missing headers. [Tobie Langel]
+
 * Ensure $A creates an empty array when its argument's length is undefined. Closes #10574. [henryju, Tobie Langel]
 
 * Fix incorrect variable declaration in Event.fire. Closes #10329. [rubley]
diff --git a/src/ajax.js b/src/ajax.js
index dc1aa99..90c4a83 100644
--- a/src/ajax.js
+++ b/src/ajax.js
@@ -209,7 +209,8 @@ Ajax.Request = Class.create(Ajax.Base, {
   
   getHeader: function(name) {
     try {
-      return this.transport.getResponseHeader(name);
+      var header = this.transport.getResponseHeader(name);
+      return Object.isUndefined(header) ? null : header;
     } catch (e) { return null }
   },