diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 614cec7..2d515d2 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -3059,7 +3059,7 @@ function _system_rebuild_theme_data() {
 
   // Set defaults for theme info.
   $defaults = array(
-    'engine' => 'phptemplate',
+    'engine' => 'twig',
     'regions' => array(
       'sidebar_first' => 'Left sidebar',
       'sidebar_second' => 'Right sidebar',