diff --git a/doc/api/crypto.rst b/doc/api/crypto.rst
index 4d3961c..7c77b03 100644
--- a/doc/api/crypto.rst
+++ b/doc/api/crypto.rst
@@ -235,6 +235,8 @@
     Return the signature algorithm used in the certificate.  If the algorithm is
     undefined, raise :py:data:`ValueError`.
 
+    ..versionadded:: 0.13
+
 
 .. py:method:: X509.get_subject()