Add :term:s for "new-style class".
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index beecc7c..078293c 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -1082,6 +1082,7 @@
 .. % Types
 .. % =========================================================================
 
+.. _newstyle:
 
 New-style and classic classes
 =============================