diff -up filefield_sources_original/filefield_sources.module filefield_sources/filefield_sources.module
--- filefield_sources_original/filefield_sources.module	2010-03-13 02:00:59.000000000 +0100
+++ filefield_sources/filefield_sources.module	2010-07-22 21:53:21.316135232 +0200
@@ -314,6 +314,7 @@ function filefield_sources_element_valid
   else {
     foreach ($validators as $function => $args) {
       array_unshift($args, $file);
+      $args[0] = &$file;
       $errors = array_merge($errors, call_user_func_array($function, $args));
     }
   }