diff --git a/snappymail/v/0.0.0/app/libraries/RainLoop/ActionsAdmin.php b/snappymail/v/0.0.0/app/libraries/RainLoop/ActionsAdmin.php
index 6f95ce0fa..6a86c1bcc 100644
--- a/snappymail/v/0.0.0/app/libraries/RainLoop/ActionsAdmin.php
+++ b/snappymail/v/0.0.0/app/libraries/RainLoop/ActionsAdmin.php
@@ -313,6 +313,7 @@ class ActionsAdmin extends Actions
 
 	public function DoAdminUpgradeCore() : array
 	{
+		\header('Connection: close');
 		return $this->DefaultResponse(\SnappyMail\Upgrade::core());
 	}