diff --git a/config.inc.php b/config.inc.php
index 5b82d0e..f00b2f4 100644
--- a/config.inc.php
+++ b/config.inc.php
@@ -5,6 +5,7 @@ use Exception;
 $GLOBALS['CONFIG_BASE_DIRS'] = array();
 $GLOBALS['CONFIG_INIT_WORKER_FUNC'] = null;
 $GLOBALS['CONFIG_FILTER_FN'] = null;
+$GLOBALS['CONFIG_BASE_CLASS'] = '\ConfBase';
 
 task('config_worker', function(array $args)
 {
@@ -870,6 +871,9 @@ function config_load_ex($conf_dir, $file, array $arr, $id = null)
     if(!class_exists($klass))
       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']}'");
+
     $cnf->import($arr, true);
   }
   catch(Exception $e)