diff --git a/mysite/_config.php b/mysite/_config.php
index 9a6665b..8bebc01 100644
--- a/mysite/_config.php
+++ b/mysite/_config.php
@@ -15,5 +15,5 @@ MySQLDatabase::set_connection_charset('utf8');
 SSViewer::set_theme('blackcandy');
 
 // enable nested URLs for this site (e.g. page/sub-page/)
-SiteTree::enable_nested_urls();
+if(class_exists('SiteTree')) SiteTree::enable_nested_urls();