diff --git a/htdocs/public/webportal/css/themes/custom.css.php b/htdocs/public/webportal/css/themes/custom.css.php
index bdb1de8d7bb..d1d20c474d8 100644
--- a/htdocs/public/webportal/css/themes/custom.css.php
+++ b/htdocs/public/webportal/css/themes/custom.css.php
@@ -45,6 +45,9 @@ if (!defined('NOREQUIREAJAX')) {
 
 session_cache_limiter('public');
 
+if (!defined('MAIN_INC_REL_DIR')) {
+	define('MAIN_INC_REL_DIR', '../../');
+}
 require_once __DIR__.'/../../webportal.main.inc.php';
 dol_include_once('/webportal/class/webPortalTheme.class.php');
 
diff --git a/htdocs/public/webportal/webportal.main.inc.php b/htdocs/public/webportal/webportal.main.inc.php
index 3fbe5b3d825..cbf21f95219 100644
--- a/htdocs/public/webportal/webportal.main.inc.php
+++ b/htdocs/public/webportal/webportal.main.inc.php
@@ -76,8 +76,11 @@ if (!function_exists('dol_getprefix')) {
 	}
 }
 
-
-include '../../main.inc.php';
+$relDir = '';
+if (defined('MAIN_INC_REL_DIR')) {
+	$relDir = MAIN_INC_REL_DIR;
+}
+include $relDir.'../../main.inc.php';
 
 require_once DOL_DOCUMENT_ROOT . '/user/class/user.class.php';
 require_once DOL_DOCUMENT_ROOT . '/societe/class/societeaccount.class.php';