diff --git a/public/include/classes/api.class.php b/public/include/classes/api.class.php
index 8e245a220..913a1f033 100644
--- a/public/include/classes/api.class.php
+++ b/public/include/classes/api.class.php
@@ -15,6 +15,7 @@ function isActive($error=true) {
       return true;
     } else {
       if ($error == true) {
+        unset($_SESSION['POPUP']);
         header('HTTP/1.1 501 Not implemented');
         die('501 Not implemented');
       }