diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index ee8ea85..89955cf 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -231,8 +231,11 @@
 does an index lookup using :func:`__getitem__`.
 
 .. versionchanged:: 3.1
-   The positional argument specifiers can be omitted, so ``'{} {}'`` is
-   equivalent to ``'{0} {1}'``.
+   The positional argument specifiers can be omitted for :meth:`str.format`,
+   so ``'{} {}'.format(a, b)`` is equivalent to ``'{0} {1}'.format(a, b)``.
+
+.. versionchanged:: 3.4
+   The positional argument specifiers can be omitted for :class:`Formatter`.
 
 Some simple format string examples::