Use https:// URLs when referring to python.org hosts.
diff --git a/Doc/tutorial/classes.rst b/Doc/tutorial/classes.rst
index 11e07e3..e318c09 100644
--- a/Doc/tutorial/classes.rst
+++ b/Doc/tutorial/classes.rst
@@ -643,7 +643,7 @@
class can be subclassed 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: