Added ::versionadded 1.1 tag to get_extension_for_class
diff --git a/docs/x509/reference.rst b/docs/x509/reference.rst
index efc2c8a..62bdb3a 100644
--- a/docs/x509/reference.rst
+++ b/docs/x509/reference.rst
@@ -891,6 +891,8 @@
 
     .. method:: get_extension_for_class(extclass)
 
+        .. versionadded:: 1.1
+
         :param extclass: An extension class.
 
         :returns: An instance of the extension class.