diff -r 346c88efed21 -r 5e2f62d02dcd wp/wp-includes/feed-atom.php
--- a/wp/wp-includes/feed-atom.php	Mon Jun 08 16:11:51 2015 +0000
+++ b/wp/wp-includes/feed-atom.php	Tue Jun 09 03:35:32 2015 +0200
@@ -8,7 +8,11 @@
 header('Content-Type: ' . feed_content_type('atom') . '; charset=' . get_option('blog_charset'), true);
 $more = 1;
 
-echo '<?xml version="1.0" encoding="'.get_option('blog_charset').'"?'.'>'; ?>
+echo '<?xml version="1.0" encoding="'.get_option('blog_charset').'"?'.'>';
+
+/** This action is documented in wp-includes/feed-rss2.php */
+do_action( 'rss_tag_pre', 'atom' );
+?>
 <feed
   xmlns="http://www.w3.org/2005/Atom"
   xmlns:thr="http://purl.org/syndication/thread/1.0"