The buffer protocol doesn't exist (in the glossary anyway).
diff --git a/Doc/library/hmac.rst b/Doc/library/hmac.rst
index 2ea3fc6..a8ca3af 100644
--- a/Doc/library/hmac.rst
+++ b/Doc/library/hmac.rst
@@ -74,7 +74,7 @@
timing analysis, making it appropriate for cryptography. *a* and *b*
must both be of the same type: either :class:`str` (ASCII only, as e.g.
returned by :meth:`HMAC.hexdigest`), or any type that supports the
- :term:`buffer protocol` (e.g. :class:`bytes`).
+ buffer protocol (e.g. :class:`bytes`).
.. note::
If *a* and *b* are different lengths, or if an error occurs,