Fix the wrong numbering of a PEP.
diff --git a/Doc/library/importlib.rst b/Doc/library/importlib.rst
index 71756e3..eb2f28a 100644
--- a/Doc/library/importlib.rst
+++ b/Doc/library/importlib.rst
@@ -54,7 +54,7 @@
     :pep:`366`
         Main module explicit relative imports
 
-    :pep:`3128`
+    :pep:`3120`
         Using UTF-8 as the Default Source Encoding