--- includes/xmlrpcs.inc	2010-08-12 11:56:59.000000000 +0200
+++ includes/xmlrpcs.inc	2010-08-12 11:57:49.000000000 +0200
@@ -38,7 +38,12 @@ function xmlrpc_server($callbacks) {
   // We build an array of all method names by combining the built-ins
   // with those defined by modules implementing the _xmlrpc hook.
   // Built-in methods are overridable.
-  foreach (array_merge($defaults, (array)$callbacks) as $key => $callback) {
+
+  // @link http://drupal.org/node/656266 @endlink
+  $callbacks = array_merge($defaults, (array)$callbacks);
+  drupal_alter('xmlrpc', $callbacks);
+
+  foreach ($callbacks as $key => $callback) {
     // we could check for is_array($callback)
     if (is_int($key)) {
       $method = $callback[0];