diff --git a/system/CodeIgniter.php b/system/CodeIgniter.php
index d9777133ba12..e7b14a96f170 100644
--- a/system/CodeIgniter.php
+++ b/system/CodeIgniter.php
@@ -947,7 +947,7 @@ protected function display404errors(PageNotFoundException $e)
         }
 
         throw PageNotFoundException::forPageNotFound(
-            (ENVIRONMENT !== 'production' || ! $this->isWeb()) ? $e->getMessage() : ''
+            (ENVIRONMENT !== 'production' || ! $this->isWeb()) ? $e->getMessage() : null
         );
     }