diff --git a/install-dev/init.php b/install-dev/init.php
index d7d1fa3dd..4324a78d6 100644
--- a/install-dev/init.php
+++ b/install-dev/init.php
@@ -43,7 +43,7 @@ require_once(_PS_INSTALL_PATH_ . 'install_version.php');
 // we check if theses constants are defined
 // in order to use init.php in upgrade.php script
 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__', substr($_SERVER['REQUEST_URI'], 0, -1 * (strlen($_SERVER['REQUEST_URI']) - strrpos($_SERVER['REQUEST_URI'], '/')) - strlen(substr(dirname($_SERVER['REQUEST_URI']), strrpos(dirname($_SERVER['REQUEST_URI']), '/') + 1))));
 
 if (!defined('_THEME_NAME_'))
 	define('_THEME_NAME_', 'default');