--- genshi/output.py~	2011-11-19 22:03:46.000000000 +0100
+++ genshi/output.py	2011-11-19 22:03:46.000000000 +0100
@@ -347,8 +347,6 @@
                 for attr, value in attrib:
                     if attr in boolean_attrs:
                         value = attr
-                    elif attr == 'xml:lang' and 'lang' not in attrib:
-                        buf += [' lang="', escape(value), '"']
                     elif attr == 'xml:space':
                         continue
                     buf += [' ', attr, '="', escape(value), '"']
--- genshi/tests/output.py~	2011-11-19 23:05:04.000000000 +0100
+++ genshi/tests/output.py	2011-11-19 23:05:05.000000000 +0100
@@ -226,7 +226,7 @@
     def test_xml_lang(self):
         text = '<p xml:lang="en">English text</p>'
         output = XML(text).render(XHTMLSerializer, encoding=None)
-        self.assertEqual('<p lang="en" xml:lang="en">English text</p>', output)
+        self.assertEqual('<p xml:lang="en">English text</p>', output)
 
     def test_xml_lang_nodup(self):
         text = '<p xml:lang="en" lang="en">English text</p>'