diff --git a/Doc/library/mailbox.rst b/Doc/library/mailbox.rst
index 60964439e4ee03..fa5b273093f583 100644
--- a/Doc/library/mailbox.rst
+++ b/Doc/library/mailbox.rst
@@ -644,7 +644,7 @@ Supported mailbox formats are Maildir, mbox, MH, Babyl, and MMDF.
    :class:`!MH` instances have all of the methods of :class:`Mailbox` in addition
    to the following:
 
-   .. versionchanged:: 3.12
+   .. versionchanged:: 3.13
 
       Supported folders that don't contain a :file:`.mh_sequences` file.