diff --git a/h5p.classes.php b/h5p.classes.php
index 9ca296a..97ee2de 100644
--- a/h5p.classes.php
+++ b/h5p.classes.php
@@ -580,7 +580,7 @@ class H5PValidator {
   // Schemas used to validate the h5p files
   private $h5pRequired = array(
     'title' => '/^.{1,255}$/',
-    'language' => '/^[/-,a-z]{1,5}$/',
+    'language' => '/^[-a-zA-Z]{1,10}$/',
     'preloadedDependencies' => array(
       'machineName' => '/^[\w0-9\-\.]{1,255}$/i',
       'majorVersion' => '/^[0-9]{1,5}$/',