diff --git a/docs/hazmat/primitives/hmac.rst b/docs/hazmat/primitives/hmac.rst
index aec406b..bfbe325 100644
--- a/docs/hazmat/primitives/hmac.rst
+++ b/docs/hazmat/primitives/hmac.rst
@@ -21,9 +21,10 @@
 .. class:: cryptography.hazmat.primitives.hmac.HMAC(key, msg=None, digestmod=None)
 
     HMAC objects take a ``key``, a hash class derived from
-    :class:`~cryptography.primitives.hashes.BaseHash`, and optional msg.  The
-    ``key`` should be randomly generated bytes and the length of the
-    ``block_size`` of the hash. You must keep the ``key`` secret.
+    :class:`~cryptography.primitives.hashes.BaseHash`, and optional message.
+    The ``key`` should be randomly generated bytes and is recommended to be
+    equal in length to the ``digest_size`` of the hash function chosen.
+    You must keep the ``key`` secret.
 
     .. doctest::
 
@@ -35,7 +36,7 @@
 
     .. method:: update(msg)
 
-        :param bytes msg: The bytes you wish to hash.
+        :param bytes msg: The bytes to hash and authenticate.
 
     .. method:: copy()