Index: template.php
===================================================================
--- template.php	(revision 36)
+++ template.php	(working copy)
@@ -151,6 +151,9 @@
   if (theme_get_setting('zen_wireframes')) {
     $classes[] = 'with-wireframes'; // Optionally add the wireframes style.
   }
+  if ($vars['language']) {
+    $classes[] = 'language-' . $vars['language']->language;
+  }
   $vars['body_classes_array'] = $classes;
   $vars['body_classes'] = implode(' ', $classes); // Concatenate with spaces.
 }