diff --git a/src/Pluf/Form/Field/File.php b/src/Pluf/Form/Field/File.php
index 5a1134e..a161884 100644
--- a/src/Pluf/Form/Field/File.php
+++ b/src/Pluf/Form/Field/File.php
@@ -37,6 +37,11 @@ class Pluf_Form_Field_File extends Pluf_Form_Field
     function clean($value)
     {
         parent::clean($value);
+        if (is_null($value) and !$this->required) {
+            return ''; // no file
+        } elseif (is_null($value) and $this->required) {
+            throw new Pluf_Form_Invalid(__('No files were uploaded. Please try to send the file again.'));
+        }
         $errors = array();
         $no_files = false;
         switch ($value['error']) {
diff --git a/src/Pluf/Utils.php b/src/Pluf/Utils.php
index 256acb9..19e63ae 100644
--- a/src/Pluf/Utils.php
+++ b/src/Pluf/Utils.php
@@ -79,7 +79,6 @@ class Pluf_Utils
      */
     static function cleanFileName($name)
     {
-        $name = mb_strtolower($name, 'UTF-8');
         return mb_ereg_replace("/\015\012|\015|\012|\s|[^A-Za-z0-9\.\-\_]/", '_', $name);
     }