diff --git a/src/IDF/Form/Admin/UserUpdate.php b/src/IDF/Form/Admin/UserUpdate.php
index 6af03f2..a5b6502 100644
--- a/src/IDF/Form/Admin/UserUpdate.php
+++ b/src/IDF/Form/Admin/UserUpdate.php
@@ -180,8 +180,11 @@ class IDF_Form_Admin_UserUpdate  extends Pluf_Form
     {
         $first_name = trim($this->cleaned_data['first_name']);
         if ($first_name == mb_strtoupper($first_name)) {
-            return mb_convert_case(mb_strtolower($first_name), 
-                                   MB_CASE_TITLE, 'UTF-8');
+            $first_name = mb_convert_case(mb_strtolower($first_name), 
+                                          MB_CASE_TITLE, 'UTF-8');
+        }
+        if ($first_name == '---') {
+            throw new Pluf_Form_Invalid(__('--- is not a valid first name.'));
         }
         return $first_name;
     }