diff --git a/drupalorg_drush.drush.inc b/drupalorg_drush.drush.inc
index 9badb80..4541ccf 100644
--- a/drupalorg_drush.drush.inc
+++ b/drupalorg_drush.drush.inc
@@ -406,7 +406,7 @@ class DrushMakeDo_ContribProjectWhitelist extends DrushMakeDo_ProjectWhitelist {
  */
 class DrushMakeDo_DownloadWhitelist extends DrushMakeDo_Whitelist {
   // The list of currently allowed project-download-level attributes.
-  protected $attribute_whitelist = array('revision', 'branch', 'tag', 'type', 'url');
+  protected $attribute_whitelist = array('revision', 'branch', 'tag', 'type', 'url', 'subtree');
 
   /**
    * Need special handling for the type attribute (it can be set, but