Add version in the doc
diff --git a/docs/hazmat/primitives/padding.rst b/docs/hazmat/primitives/padding.rst
index 475976a..0b76327 100644
--- a/docs/hazmat/primitives/padding.rst
+++ b/docs/hazmat/primitives/padding.rst
@@ -56,6 +56,8 @@
.. class:: ANSIX923(block_size)
+ .. versionadded:: 1.3
+
`ANSI X.923`_ padding works by appending ``N-1`` bytes with the value of
``0`` and a last byte with the value of ``chr(N)``, where ``N`` is the
number of bytes required to make the final block of data the same size as