diff --git a/entity_boxes_type.admin.inc b/entity_boxes_type.admin.inc
index 109ea40..9046de4 100644
--- a/entity_boxes_type.admin.inc
+++ b/entity_boxes_type.admin.inc
@@ -42,12 +42,12 @@ function entity_boxes_type_form($form, &$form_state, $entity_boxes_type, $op = '
   $form['type'] = array(
     '#type' => 'machine_name',
     '#default_value' => isset($entity_boxes_type->type) ? $entity_boxes_type->type : '',
-    '#maxlength' => 32,
+    '#maxlength' => 21,
     '#machine_name' => array(
       'exists' => 'entity_boxes_get_types',
       'source' => array('label'),
     ),
-    '#description' => t('A unique machine-readable name for this entity_boxes type. It must only contain lowercase letters, numbers, and underscores.'),
+    '#description' => t('A unique machine-readable name for this entity_boxes type. It must only contain lowercase letters, numbers, underscores and be 21 characters or less.'),
   );
 
   $form['actions'] = array('#type' => 'actions');