Index: lxml-5.1.0/src/lxml/tests/test_etree.py
===================================================================
--- lxml-5.1.0.orig/src/lxml/tests/test_etree.py
+++ lxml-5.1.0/src/lxml/tests/test_etree.py
@@ -3256,6 +3256,7 @@ class ETreeOnlyTestCase(HelperTestCase):
         self.assertEqual(re, e.nsmap)
         self.assertEqual(r,  s.nsmap)
 
+    @unittest.skipIf(etree.LIBXML_VERSION >= (2, 10, 4), "libxml2 regression ignores namespaces")
     def test_html_prefix_nsmap(self):
         etree = self.etree
         el = etree.HTML('<hha:page-description>aa</hha:page-description>')