add versionadded to cast5
diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index 210e656..d91dde9 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -117,6 +117,8 @@
.. class:: CAST5(key)
+ .. versionadded:: 0.2
+
CAST5 (also known as CAST-128) is a block cipher approved for use in the
Canadian government by the `Communications Security Establishment`_. It is
a variable key length cipher and supports keys from 40-128 bits in length.