Fixed sizeof tests for ElementTree (issue #23450).
diff --git a/Lib/test/test_xml_etree_c.py b/Lib/test/test_xml_etree_c.py
index 816aa86..d0df38d 100644
--- a/Lib/test/test_xml_etree_c.py
+++ b/Lib/test/test_xml_etree_c.py
@@ -55,7 +55,7 @@
     def setUp(self):
         self.elementsize = support.calcobjsize('5P')
         # extra
-        self.extra = struct.calcsize('PiiP4P')
+        self.extra = struct.calcsize('PnnP4P')
 
     check_sizeof = support.check_sizeof