diff --git a/includes/xmlrpcs.inc b/includes/xmlrpcs.inc
index 7fb4ca895e2b8b9d630b43e93e89a20f16a35907..fd5a40733f6f49f4b306b124818e2ef15ca81d60 100644
--- a/includes/xmlrpcs.inc
+++ b/includes/xmlrpcs.inc
@@ -45,7 +45,9 @@ 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) {
+  $callbacks = array_merge($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];
diff --git a/modules/simpletest/tests/xmlrpc.test b/modules/simpletest/tests/xmlrpc.test
index 7aad2be11a06e29ab84a0787386d91f3c0d30647..5069fe2467c5c1def15db08b4a7373afe31e393e 100644
--- a/modules/simpletest/tests/xmlrpc.test
+++ b/modules/simpletest/tests/xmlrpc.test
@@ -188,8 +188,8 @@ class XMLRPCValidator1IncTestCase extends DrupalWebTestCase {
 class XMLRPCMessagesTestCase extends DrupalWebTestCase {
   public static function getInfo() {
     return array(
-      'name'  => 'XML-RPC message',
-      'description' => 'Test large messages.',
+      'name'  => 'XML-RPC message and alteration',
+      'description' => 'Test large messages and method alterations.',
       'group' => 'XML-RPC',
     );
   }
@@ -211,4 +211,25 @@ class XMLRPCMessagesTestCase extends DrupalWebTestCase {
       $this->assertEqual($xml_message_l, $xml_message_r, t('XML-RPC messages.messageSizedInKB of %s Kb size received', array('%s' => $size)));
     }
   }
+
+  /**
+   * Ensure that hook_xmlrpc_alter() can hide even builtin methods.
+   */
+  protected function testAlterListMethods() {
+
+    // Ensure xmlrpc_test_xmlrpc_alter() is disabled and retrieve regular list of methods.
+    variable_set('xmlrpc_test_xmlrpc_alter', FALSE);
+    $url = url(NULL, array('absolute' => TRUE)) . 'xmlrpc.php';
+    $methods1 = xmlrpc($url, array('system.listMethods' => array()));
+
+    // Enable the alter hook and retrieve the list of methods again.
+    variable_set('xmlrpc_test_xmlrpc_alter', TRUE);
+    $methods2 = xmlrpc($url, array('system.listMethods' => array()));
+
+    $diff = array_diff($methods1, $methods2);
+    $this->assertTrue(is_array($diff) && !empty($diff), t('Method list is altered by hook_xmlrpc_alter'));
+    $removed = reset($diff);
+    $this->assertEqual($removed, 'system.methodSignature', t('Hiding builting system.methodSignature with hook_xmlrpc_alter works'));
+  }
+
 }
diff --git a/modules/simpletest/tests/xmlrpc_test.module b/modules/simpletest/tests/xmlrpc_test.module
index 9f06f48ae73a3b49fccd17528b7714a469b3044f..f52afe325ee58e11fa5d800e6382f1aead9785d5 100644
--- a/modules/simpletest/tests/xmlrpc_test.module
+++ b/modules/simpletest/tests/xmlrpc_test.module
@@ -63,6 +63,29 @@ function xmlrpc_test_xmlrpc() {
   );
 }
 
+/**
+ * Implements hook_xmlrpc_alter().
+ *
+ * Hide (or not) the system.methodSignature() service depending on a variable.
+ */
+function xmlrpc_test_xmlrpc_alter(&$services) {
+  if (variable_get('xmlrpc_test_xmlrpc_alter', FALSE)) {
+    $remove = NULL;
+    foreach ($services as $key => $value) {
+      if (!is_array($value)) {
+        continue;
+      }
+      if ($value[0] == 'system.methodSignature') {
+        $remove = $key;
+        break;
+      }
+    }
+    if (isset($remove)) {
+      unset($services[$remove]);
+    }
+  }
+}
+
 /**
  * Created a message of the desired size in KB.
  *
diff --git a/modules/system/system.api.php b/modules/system/system.api.php
index c497871e5be2957723b18ddc038f999545b43b32..2e420dc6f089eb915fc9cb6c65fbb3a5b731036c 100644
--- a/modules/system/system.api.php
+++ b/modules/system/system.api.php
@@ -1954,37 +1954,33 @@ function hook_xmlrpc() {
 }
 
 /**
- * Alter the definition of XML-RPC methods before they are called.
+ * Alters the definition of XML-RPC methods before they are called.
  *
- * This hook lets at module modify the callback definition for already
- * declared XML-RPC methods, when they are being invoked by a client.
+ * This hook allows modules to modify the callback definition of declared
+ * XML-RPC methods, right before they are invoked by a client. Methods may be
+ * added, or existing methods may be altered.
  *
- * This hook is invoked by xmlrpc.php. The method definitions are
- * passed in by reference. Each element of the $methods array is one
- * callback definition returned by a module from hook_xmlrpc. Additional
- * methods may be added, or existing items altered.
- *
- * Modules implementing this hook must take care of the fact that
- * hook_xmlrpc allows two distinct and incompatible formats for callback
- * definition, so module must be prepared to handle either format for
- * each callback being altered.
+ * Note that hook_xmlrpc() supports two distinct and incompatible formats to
+ * define a callback, so care must be taken when altering other methods.
  *
  * @param $methods
- *   Associative array of method callback definitions returned from
- *   hook_xmlrpc.
+ *   An asssociative array of method callback definitions, as returned from
+ *   hook_xmlrpc() implementations.
  *
  * @see hook_xmlrpc()
+ * @see xmlrpc_server()
  */
 function hook_xmlrpc_alter(&$methods) {
-
-  // Direct update for methods defined the simple way
+  // Directly change a simple method.
   $methods['drupal.login'] = 'mymodule_login';
 
-  // Lookup update for methods defined the complex way
+  // Alter complex definitions.
   foreach ($methods as $key => &$method) {
+    // Skip simple method definitions.
     if (!is_int($key)) {
       continue;
     }
+    // Perform the wanted manipulation.
     if ($method[0] == 'drupal.site.ping') {
       $method[1] = 'mymodule_directory_ping';
     }
diff --git a/xmlrpc.php b/xmlrpc.php
index 5787f5b195a1074b97822d8a4e1aabad54e56582..4b6b1153fcef211b6de2243ff71d8b472970c6e7 100644
--- a/xmlrpc.php
+++ b/xmlrpc.php
@@ -16,6 +16,4 @@
 include_once DRUPAL_ROOT . '/includes/xmlrpc.inc';
 include_once DRUPAL_ROOT . '/includes/xmlrpcs.inc';
 
-$services = module_invoke_all('xmlrpc');
-drupal_alter('xmlrpc', $services);
-xmlrpc_server($services);
+xmlrpc_server(module_invoke_all('xmlrpc'));