Index: wp-includes/class-wp-theme.php
===================================================================
--- wp-includes/class-wp-theme.php	(revision 21733)
+++ wp-includes/class-wp-theme.php	(working copy)
@@ -41,6 +41,7 @@
 		'default'      => 'WordPress Default',
 		'twentyten'    => 'Twenty Ten',
 		'twentyeleven' => 'Twenty Eleven',
+		'twentytwelve' => 'Twenty Twelve',
 	);
 
 	/**
Index: wp-includes/default-constants.php
===================================================================
--- wp-includes/default-constants.php	(revision 21733)
+++ wp-includes/default-constants.php	(working copy)
@@ -296,6 +296,6 @@
 	 * @since 3.0.0
 	 */
 	if ( !defined('WP_DEFAULT_THEME') )
-		define( 'WP_DEFAULT_THEME', 'twentyeleven' );
+		define( 'WP_DEFAULT_THEME', 'twentytwelve' );
 
 }
Index: wp-admin/includes/update-core.php
===================================================================
--- wp-admin/includes/update-core.php	(revision 21733)
+++ wp-admin/includes/update-core.php	(working copy)
@@ -559,7 +559,8 @@
 $_new_bundled_files = array(
 'plugins/akismet/' => '2.0',
 'themes/twentyten/' => '3.0',
-'themes/twentyeleven/' => '3.2'
+'themes/twentyeleven/' => '3.2',
+'themes/twentytwelve/' => '3.5'
 );
 
 /**