--- a/yslt.yml2	Sat Dec 10 10:11:31 2016 +0100
+++ b/yslt.yml2	Tue Apr 25 17:44:53 2017 +0200
@@ -39,6 +39,7 @@
         xmlns:str='http://exslt.org/strings',
         xmlns:dyn='http://exslt.org/dynamic',
         xmlns:set='http://exslt.org/sets',
+        xmlns:sets='http://exslt.org/sets',
         xmlns:date='http://exslt.org/dates-and-times',
         xmlns:yml='http://fdik.org/yml',
         extension-element-prefixes='exsl func str dyn set math date yml'