Doc: replace PEP xxx by :pep:`xxx` to create a link on the PEP
diff --git a/Doc/howto/cporting.rst b/Doc/howto/cporting.rst
index 9b66650..c0b5933 100644
--- a/Doc/howto/cporting.rst
+++ b/Doc/howto/cporting.rst
@@ -118,7 +118,7 @@
Module initialization and state
===============================
-Python 3.0 has a revamped extension module initialization system. (See PEP
+Python 3.0 has a revamped extension module initialization system. (See
:pep:`3121`.) Instead of storing module state in globals, they should be stored
in an interpreter specific structure. Creating modules that act correctly in
both 2.x and 3.0 is tricky. The following simple example demonstrates how. ::