Use https:// URLs when referring to python.org hosts.
diff --git a/Doc/tutorial/classes.rst b/Doc/tutorial/classes.rst
index 77c050b..8970a66 100644
--- a/Doc/tutorial/classes.rst
+++ b/Doc/tutorial/classes.rst
@@ -600,7 +600,7 @@
without affecting the precedence order of its parents). Taken together, these
properties make it possible to design reliable and extensible classes with
multiple inheritance. For more detail, see
-http://www.python.org/download/releases/2.3/mro/.
+https://www.python.org/download/releases/2.3/mro/.
.. _tut-private: