diff --git a/config.inc.php b/config.inc.php
index 849b044..4fb2d75 100644
--- a/config.inc.php
+++ b/config.inc.php
@@ -394,7 +394,7 @@ function _config_invalidate_cache($file, $cache_file) : ConfigCacheEntry
 
   $pres = config_parse(config_base_dir(), $file);
   if($pres->error !== 0)
-    throw new Exception("Error({$pres->error}) while loading JSON from {$file}:\n" . $pres->error_descr);
+    throw new Exception("Error({$pres->error}) while loading JSON in file '{$file}':\n" . $pres->error_descr);
 
   $includes = config_get_module_includes($pres->jsm_module);
 
@@ -740,7 +740,7 @@ function config_check_and_decode_jzon($json)
 function config_load_ex($conf_dir, $file, array $arr, $id = null)
 {
   if(!isset($arr['class']) || !isset($arr['class'][0]))
-    throw new Exception("Class is not set. File '$file'.");
+    throw new Exception("Class is not set in file '$file'.");
 
   $klass = $arr['class'];
   unset($arr['class']);
@@ -751,12 +751,14 @@ function config_load_ex($conf_dir, $file, array $arr, $id = null)
   $cnf = null;
   try
   {
+    if(!class_exists($klass))
+      throw new Exception("No such class '$klass'");
     $cnf = new $klass;   
     $cnf->import($arr, true);
   }
   catch(Exception $e)
   {
-    throw new Exception($e->getMessage() . ". File '{$file}'"/* . $e->getTraceAsString()*/);
+    throw new Exception($e->getMessage() . " in file '{$file}'"/* . $e->getTraceAsString()*/);
   }
   
   $cnf->id = $id;