diff --git a/library/Zend/Cache.php b/library/Zend/Cache.php
index 402bcfa..74d365d 100644
--- a/library/Zend/Cache.php
+++ b/library/Zend/Cache.php
@@ -202,7 +202,7 @@ public static function _makeFrontend($frontend, $frontendOptions = array(), $cus
      * @param  string $msg  Message for the exception
      * @throws Zend_Cache_Exception
      */
-    public static function throwException($msg, Exception $e = null)
+    public static function throwException($msg, ?Exception $e = null)
     {
         // For perfs reasons, we use this dynamic inclusion
         #require_once 'Zend/Cache/Exception.php';