diff --git a/Doc/library/hmac.rst b/Doc/library/hmac.rst
index c2066a7..4c707e9 100644
--- a/Doc/library/hmac.rst
+++ b/Doc/library/hmac.rst
@@ -16,20 +16,26 @@
 
 .. function:: new(key, msg=None, digestmod=None)
 
-   Return a new hmac object.  *key* is a bytes object giving the secret key.  If
-   *msg* is present, the method call ``update(msg)`` is made.  *digestmod* is
-   the digest constructor or module for the HMAC object to use. It defaults to
-   the :func:`hashlib.md5` constructor.
+   Return a new hmac object.  *key* is a bytes or bytearray object giving the
+   secret key.  If *msg* is present, the method call ``update(msg)`` is made.
+   *digestmod* is the digest constructor or module for the HMAC object to use.
+   It defaults to the :func:`hashlib.md5` constructor.
 
+   .. versionchanged:: 3.4
+      Parameter *key* can be a bytes or bytearray object. Parameter *msg* can
+      be of any type supported by :mod:`hashlib`.
 
 An HMAC object has the following methods:
 
 .. method:: HMAC.update(msg)
 
-   Update the hmac object with the bytes object *msg*.  Repeated calls are
-   equivalent to a single call with the concatenation of all the arguments:
+   Update the hmac object with *msg*.  Repeated calls are equivalent to a
+   single call with the concatenation of all the arguments:
    ``m.update(a); m.update(b)`` is equivalent to ``m.update(a + b)``.
 
+   .. versionchanged:: 3.4
+      Parameter *msg* can be of any type supported by :mod:`hashlib`.
+
 
 .. method:: HMAC.digest()
 
diff --git a/Lib/hmac.py b/Lib/hmac.py
index 6bd0de5..d13b205 100644
--- a/Lib/hmac.py
+++ b/Lib/hmac.py
@@ -31,11 +31,11 @@
                    A hashlib constructor returning a new hash object.
                    Defaults to hashlib.md5.
 
-        Note: key and msg must be bytes objects.
+        Note: key and msg must be a bytes or bytearray objects.
         """
 
-        if not isinstance(key, bytes):
-            raise TypeError("key: expected bytes, but got %r" % type(key).__name__)
+        if not isinstance(key, (bytes, bytearray)):
+            raise TypeError("key: expected bytes or bytearray, but got %r" % type(key).__name__)
 
         if digestmod is None:
             import hashlib
@@ -75,8 +75,6 @@
     def update(self, msg):
         """Update this hashing object with the string msg.
         """
-        if not isinstance(msg, bytes):
-            raise TypeError("expected bytes, but got %r" % type(msg).__name__)
         self.inner.update(msg)
 
     def copy(self):
diff --git a/Lib/test/test_hmac.py b/Lib/test/test_hmac.py
index 4ca7cec..efd63ad 100644
--- a/Lib/test/test_hmac.py
+++ b/Lib/test/test_hmac.py
@@ -253,6 +253,20 @@
         except:
             self.fail("Constructor call with text argument raised exception.")
 
+    def test_with_bytearray(self):
+        try:
+            h = hmac.HMAC(bytearray(b"key"), bytearray(b"hash this!"))
+            self.assertEqual(h.hexdigest(), '34325b639da4cfd95735b381e28cb864')
+        except:
+            self.fail("Constructor call with bytearray arguments raised exception.")
+
+    def test_with_memoryview_msg(self):
+        try:
+            h = hmac.HMAC(b"key", memoryview(b"hash this!"))
+            self.assertEqual(h.hexdigest(), '34325b639da4cfd95735b381e28cb864')
+        except:
+            self.fail("Constructor call with memoryview msg raised exception.")
+
     def test_withmodule(self):
         # Constructor call with text and digest module.
         try:
diff --git a/Misc/ACKS b/Misc/ACKS
index 02c04bd..ecf081e 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -138,6 +138,7 @@
 Forest Bond
 Gregory Bond
 Matias Bordese
+Jonas Borgström
 Jurjen Bos
 Peter Bosch
 Dan Boswell
diff --git a/Misc/NEWS b/Misc/NEWS
index 137284b..92d7c39 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -135,6 +135,9 @@
 Library
 -------
 
+- Issue 18240: The HMAC module is no longer restricted to bytes and accepts
+  any bytes-like object, e.g. memoryview. Original patch by Jonas Borgström.
+
 - Issue #18224: Removed pydoc script from created venv, as it causes problems
   on Windows and adds no value over and above python -m pydoc ...