diff --git a/docs/changelog.rst b/docs/changelog.rst
index 222fee63..157ed902 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -139,12 +139,25 @@ Fixes
   0.2.3 behaviour of defaulting to Kqueue in this case, but still prefer
   :func:`select.poll` if it is available.
 
+* `#545 <https://github.com/dw/mitogen/issues/545>`_: an optimization
+  introduced in `#493 <https://github.com/dw/mitogen/issues/493>`_ caused a
+  64-bit integer to be assigned to a 32-bit field on ARM 32-bit targets,
+  causing runs to fail.
+
+
+Core Library
+~~~~~~~~~~~~
+
+* `ca63c26e <https://github.com/dw/mitogen/commit/ca63c26e>`_:
+  :meth:`mitogen.core.Latch.put`'s `obj` argument was made optional.
+
 
 Thanks!
 ~~~~~~~
 
 Mitogen would not be possible without the support of users. A huge thanks for
 bug reports, testing, features and fixes in this release contributed by
+`Fabian Arrotin <https://github.com/arrfab>`_, and
 `Petr Enkov <https://github.com/enkov>`_.
 
 
diff --git a/docs/conf.py b/docs/conf.py
index 3708a943..a6bc2cbc 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -6,7 +6,7 @@ import mitogen
 VERSION = '%s.%s.%s' % mitogen.__version__
 
 author = u'David Wilson'
-copyright = u'2018, David Wilson'
+copyright = u'2019, David Wilson'
 exclude_patterns = ['_build']
 extensions = ['sphinx.ext.autodoc', 'sphinx.ext.intersphinx', 'sphinxcontrib.programoutput']
 html_show_sourcelink = False
diff --git a/mitogen/core.py b/mitogen/core.py
index cfdf996b..25732896 100644
--- a/mitogen/core.py
+++ b/mitogen/core.py
@@ -2140,7 +2140,7 @@ class Latch(object):
             return rsock, wsock
 
     COOKIE_MAGIC, = struct.unpack('L', b('LTCH') * (struct.calcsize('L')//4))
-    COOKIE_FMT = 'Llll'
+    COOKIE_FMT = '>Qqqq'  # #545: id() and get_ident() may exceed long on armhfp.
     COOKIE_SIZE = struct.calcsize(COOKIE_FMT)
 
     def _make_cookie(self):
@@ -2240,11 +2240,14 @@ class Latch(object):
         finally:
             self._lock.release()
 
-    def put(self, obj):
+    def put(self, obj=None):
         """
         Enqueue an object, waking the first thread waiting for a result, if one
         exists.
 
+        :param obj:
+            Object to enqueue. Defaults to :data:`None` as a convenience when
+            using :class:`Latch` only for synchronization.
         :raises mitogen.core.LatchError:
             :meth:`close` has been called, and the object is no longer valid.
         """
diff --git a/tests/bench/throughput.py b/tests/bench/throughput.py
index 896ee9ac..42604826 100644
--- a/tests/bench/throughput.py
+++ b/tests/bench/throughput.py
@@ -9,6 +9,7 @@ import time
 
 import mitogen
 import mitogen.service
+import ansible_mitogen.affinity
 
 
 def prepare():
@@ -45,6 +46,8 @@ def run_test(router, fp, s, context):
 
 @mitogen.main()
 def main(router):
+    ansible_mitogen.affinity.policy.assign_muxprocess()
+
     bigfile = tempfile.NamedTemporaryFile()
     fill_with_random(bigfile, 1048576*512)
 
diff --git a/tests/serialization_test.py b/tests/serialization_test.py
index 23c4a2d9..6cf5f8b7 100644
--- a/tests/serialization_test.py
+++ b/tests/serialization_test.py
@@ -8,11 +8,23 @@ from mitogen.core import b
 import testlib
 
 
+class EvilObject(object):
+    pass
+
+
 def roundtrip(v):
     msg = mitogen.core.Message.pickled(v)
     return mitogen.core.Message(data=msg.data).unpickle()
 
 
+class EvilObjectTest(testlib.TestCase):
+    def test_deserialization_fails(self):
+        msg = mitogen.core.Message.pickled(EvilObject())
+        e = self.assertRaises(mitogen.core.StreamError,
+            lambda: msg.unpickle()
+        )
+
+
 class BlobTest(testlib.TestCase):
     klass = mitogen.core.Blob