Ticket #23819: 23819.2.diff

wp-content/themes/twentythirteen/inc/back-compat.php

@@ -15 +15 @@
         unset( $_GET['activated'] );
         add_action( 'admin_notices', 'twentythirteen_upgrade_notice' );
 }
-add_action( 'after_switch_theme', 'twentythirteen_switch_theme', 10, 2 );
+add_action( 'after_switch_theme', 'twentythirteen_compat_switch_theme', 10, 2 );
 
+/**
+ * Prevent previewing theme with Live Customizer.
+ */
+function twentythirteen_compat_customizer() {
+        if ( version_compare( $GLOBALS['wp_version'], '3.6-alpha', '>=' ) )
+                return;
+
+        wp_redirect( '/wp-admin/themes.php' );
+}
+add_action( 'load-customize.php', 'twentythirteen_compat_customizer' );
+
 function twentythirteen_upgrade_notice() {
         $message = sprintf( __( 'Twenty Thirteen requires at least WordPress version 3.6. You are running version %s. Please upgrade and try again.' ), $GLOBALS['wp_version'] );
         printf( '<div class="error"><p>%s</p></div>', $message );