address review feedback
diff --git a/docs/x509.rst b/docs/x509.rst
index 2c9c0f4..ba52d91 100644
--- a/docs/x509.rst
+++ b/docs/x509.rst
@@ -6,7 +6,8 @@
.. currentmodule:: cryptography.x509
X.509 is an ITU-T standard for a `public key infrastructure`_. X.509v3 is
-defined in :rfc:`5280` (which obsoletes :rfc:`2459` and :rfc:`3280`).
+defined in :rfc:`5280` (which obsoletes :rfc:`2459` and :rfc:`3280`). X.509
+certificates are commonly used in protocols like `TLS`_.
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@@ -92,6 +93,10 @@
For version 3 X.509 certificates.
+.. class:: InvalidX509Version
+
+ This is raised when an X.509 certificate has an invalid version number.
.. _`public key infrastructure`: https://en.wikipedia.org/wiki/Public_key_infrastructure
+.. _`TLS`: https://en.wikipedia.org/wiki/Transport_Layer_Security