diff --git a/Lib/Configuration.php b/Lib/Configuration.php
index 6421c1a..5524729 100644
--- a/Lib/Configuration.php
+++ b/Lib/Configuration.php
@@ -53,7 +53,7 @@ class Configuration {
         'www_library_id' => 2,
     );
 
-    private $custom_config = 'configuration.local.php';
+    private $custom_config_filename = 'configuration.local.php';
 
     private function __construct() {
         // by default, set the session save path to the default value;