Index: wp-includes/default-constants.php
===================================================================
--- wp-includes/default-constants.php	(revision 23934)
+++ wp-includes/default-constants.php	(working copy)
@@ -55,7 +55,7 @@
 	// Add define('WP_DEBUG_DISPLAY', null); to wp-config.php use the globally configured setting for
 	// display_errors and not force errors to be displayed. Use false to force display_errors off.
 	if ( !defined('WP_DEBUG_DISPLAY') )
-		define( 'WP_DEBUG_DISPLAY', true );
+		define( 'WP_DEBUG_DISPLAY', ! ( defined( 'XMLRPC_REQUEST' ) && XMLRPC_REQUEST ) );
 
 	// Add define('WP_DEBUG_LOG', true); to enable error logging to wp-content/debug.log.
 	if ( !defined('WP_DEBUG_LOG') )