diff --git a/setup/inc/class.setup.inc.php b/setup/inc/class.setup.inc.php
index e332a071ac..fc0013785b 100644
--- a/setup/inc/class.setup.inc.php
+++ b/setup/inc/class.setup.inc.php
@@ -253,6 +253,7 @@ class setup
 			case PHP_SESSION_DISABLED:
 				throw new \ErrorException('EGroupware requires PHP session extension!');
 			case PHP_SESSION_NONE:
+				if (headers_sent()) return false;
 				ini_set('session.use_cookie', true);
 				session_name(self::SESSIONID);
 				session_set_cookie_params(0, '/', self::cookiedomain(),