diff --git a/lib/OpenLayers/Request/XMLHttpRequest.js b/lib/OpenLayers/Request/XMLHttpRequest.js
index f5b932bcc6..db322955d9 100644
--- a/lib/OpenLayers/Request/XMLHttpRequest.js
+++ b/lib/OpenLayers/Request/XMLHttpRequest.js
@@ -249,8 +249,8 @@
         // BUGFIX: Gecko - fails sending Element (this is up to the implementation either to standard)
         if (vData && vData.nodeType) {
             vData    = window.XMLSerializer ? new window.XMLSerializer().serializeToString(vData) : vData.xml;
-            if (!oRequest._headers["Content-Type"])
-                oRequest._object.setRequestHeader("Content-Type", "application/xml");
+            if (!this._headers["Content-Type"])
+                this._object.setRequestHeader("Content-Type", "application/xml");
         }
 
         this._data    = vData;