Revert copy_reg -> copyreg rename.
diff --git a/Doc/library/persistence.rst b/Doc/library/persistence.rst
index 3708d17..78e40f6 100644
--- a/Doc/library/persistence.rst
+++ b/Doc/library/persistence.rst
@@ -19,7 +19,7 @@
 .. toctree::
 
    pickle.rst
-   copyreg.rst
+   copy_reg.rst
    shelve.rst
    marshal.rst
    anydbm.rst