Issue #18743: Improved cross-references to the StringIO class.
diff --git a/Doc/library/mailbox.rst b/Doc/library/mailbox.rst
index 3a87c13..c016564 100644
--- a/Doc/library/mailbox.rst
+++ b/Doc/library/mailbox.rst
@@ -661,7 +661,7 @@
In Babyl mailboxes, the headers of a message are not stored contiguously
with the body of the message. To generate a file-like representation, the
- headers and body are copied together into a :class:`StringIO` instance
+ headers and body are copied together into a :class:`~StringIO.StringIO` instance
(from the :mod:`StringIO` module), which has an API identical to that of a
file. As a result, the file-like object is truly independent of the
underlying mailbox but does not save memory compared to a string