Index: wp-includes/wp-db.php
===================================================================
--- wp-includes/wp-db.php	(revision 23916)
+++ wp-includes/wp-db.php	(working copy)
@@ -536,8 +536,10 @@
 	function __construct( $dbuser, $dbpassword, $dbname, $dbhost ) {
 		register_shutdown_function( array( $this, '__destruct' ) );
 
-		if ( WP_DEBUG )
+		if ( WP_DEBUG & WP_DEBUG_DISPLAY )
+		{
 			$this->show_errors();
+		}
 
 		$this->init_charset();