Index: wp-includes/class-IXR.php
===================================================================
--- wp-includes/class-IXR.php	(revision 21088)
+++ wp-includes/class-IXR.php	(working copy)
@@ -369,7 +369,9 @@
     {
         if (!$data) {
             if (isset($_SERVER['REQUEST_METHOD']) && $_SERVER['REQUEST_METHOD'] !== 'POST') {
-            	header('Content-Type: text/plain'); // merged from WP #9093
+                header("HTTP/1.1 405 Method Not Allowed");
+                header('Allow: POST');
+                header('Content-Type: text/plain'); // merged from WP #9093
                 die('XML-RPC server accepts POST requests only.');
             }