diff --git a/setup/index.php b/setup/index.php
index c98ea1d8d7..890c930e8a 100644
--- a/setup/index.php
+++ b/setup/index.php
@@ -54,5 +54,7 @@ if (!function_exists('json_decode'))
 }
 /////////////////////////////////////////////////////////////////////
 
+//N°3671 setup context: force $bForceTrustProxy to be persisted in next calls
+utils::GetAbsoluteUrlAppRoot(true);
 $oWizard = new WizardController('WizStepWelcome');
 $oWizard->Run();