diff --git a/install-dev/upgrade/upgrade.php b/install-dev/upgrade/upgrade.php
index e08746a90..3aefe2d1e 100644
--- a/install-dev/upgrade/upgrade.php
+++ b/install-dev/upgrade/upgrade.php
@@ -66,7 +66,7 @@ else
 
 // need for upgrade before 1.5
 if (!defined('__PS_BASE_URI__'))
-	define('__PS_BASE_URI__', str_replace('//', '/', '/'.trim(preg_replace('#/(install(-dev)?)$#', '/', str_replace('\\', '/', dirname($_SERVER['REQUEST_URI']))), '/').'/'));
+	define('__PS_BASE_URI__', str_replace('//', '/', '/'.trim(preg_replace('#/(install(-dev)?/upgrade)$#', '/', str_replace('\\', '/', dirname($_SERVER['REQUEST_URI']))), '/').'/'));
 
 // need for upgrade before 1.5
 if (!defined('_THEME_NAME_'))