document that the OpenSSL backend conforms to the CMACBackend interface
diff --git a/docs/hazmat/backends/openssl.rst b/docs/hazmat/backends/openssl.rst
index f15bc28..f21116b 100644
--- a/docs/hazmat/backends/openssl.rst
+++ b/docs/hazmat/backends/openssl.rst
@@ -14,6 +14,7 @@
It implements the following interfaces:
* :class:`~cryptography.hazmat.backends.interfaces.CipherBackend`
+ * :class:`~cryptography.hazmat.backends.interfaces.CMACBackend`
* :class:`~cryptography.hazmat.backends.interfaces.DSABackend`
* :class:`~cryptography.hazmat.backends.interfaces.HashBackend`
* :class:`~cryptography.hazmat.backends.interfaces.HMACBackend`