diff --git a/config.inc.php b/config.inc.php
index 64b787f..0865cf9 100644
--- a/config.inc.php
+++ b/config.inc.php
@@ -1028,7 +1028,7 @@ function config_load_ex(string $conf_dir, string $file, array $arr, ?int $id = n
       throw new Exception("No such class '$klass'");
     $cnf = new $klass;   
     if(!is_a($cnf, $GLOBALS['CONFIG_BASE_CLASS']))
-      throw new Exception("Class '$klass' must inherit from '{$GLOBALS['CONFIG_BASE_CLASS']}'");
+      throw new Exception("'$klass' is not subclass of '".ltrim($GLOBALS['CONFIG_BASE_CLASS'], '\\')."'");
 
     $cnf->import($arr, true);
   }