diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index 28b143b..950ea8b 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -79,6 +79,7 @@
 
         :param bytes data: The data you wish to pass into the context.
         :return bytes: Returns the data that was encrypted or decrypted.
+        :raises cryptography.exceptions.AlreadyFinalized: See :meth:`finalize`
 
         When the ``Cipher`` was constructed in a mode that turns it into a
         stream cipher (e.g.
@@ -90,6 +91,10 @@
 
         :return bytes: Returns the remainder of the data.
 
+        Once ``finalize`` is called this object can no longer be used and
+        :meth:`update` will raise
+        :class:`~cryptography.exceptions.AlreadyFinalized`.
+
 Algorithms
 ~~~~~~~~~~