diff --git a/mitogen/core.py b/mitogen/core.py
index dba5648b..9a9cc0a1 100644
--- a/mitogen/core.py
+++ b/mitogen/core.py
@@ -162,11 +162,27 @@ class Message(object):
     reply_to = None
     data = None
 
+    router = None
+
     def __init__(self, **kwargs):
         self.src_id = mitogen.context_id
         vars(self).update(kwargs)
 
-    _find_global = None
+    def _unpickle_context(self, context_id, name):
+        return _unpickle_context(self.router, context_id, name)
+
+    def _find_global(self, module, func):
+        """Return the class implementing `module_name.class_name` or raise
+        `StreamError` if the module is not whitelisted."""
+        if module == __name__:
+            if func == '_unpickle_call_error':
+                return _unpickle_call_error
+            elif func == '_unpickle_dead':
+                return _unpickle_dead
+            elif func == '_unpickle_context':
+                return self._unpickle_context
+
+        raise StreamError('cannot unpickle %r/%r', module, func)
 
     @classmethod
     def pickled(cls, obj, **kwargs):
@@ -182,8 +198,7 @@ class Message(object):
         IOLOG.debug('%r.unpickle()', self)
         fp = cStringIO.StringIO(self.data)
         unpickler = cPickle.Unpickler(fp)
-        if self._find_global:
-            unpickler.find_global = self._find_global
+        unpickler.find_global = self._find_global
         try:
             return unpickler.load()
         except (TypeError, ValueError), ex:
@@ -521,7 +536,6 @@ class Stream(BasicStream):
     """
     _input_buf = ''
     _output_buf = ''
-    message_class = Message
 
     def __init__(self, router, remote_id, key, **kwargs):
         self._router = router
@@ -556,7 +570,10 @@ class Stream(BasicStream):
         if len(self._input_buf) < self.HEADER_LEN:
             return False
 
-        msg = self.message_class()
+        msg = Message()
+        # To support unpickling Contexts.
+        msg.router = self._router
+
         (msg.dst_id, msg.src_id,
          msg.handle, msg.reply_to, msg_len) = struct.unpack(
             self.HEADER_FMT,
@@ -628,6 +645,9 @@ class Context(object):
         self.name = name
         self.key = key or ('%016x' % random.getrandbits(128))
 
+    def __reduce__(self):
+        return _unpickle_context, (self.context_id, self.name)
+
     def on_disconnect(self, broker):
         LOG.debug('Parent stream is gone, dying.')
         fire(self, 'disconnect')
@@ -672,6 +692,13 @@ class Context(object):
         return 'Context(%s, %r)' % (self.context_id, self.name)
 
 
+def _unpickle_context(router, context_id, name):
+    assert isinstance(router, Router)
+    assert isinstance(context_id, (int, long)) and context_id > 0
+    assert type(name) is str and len(name) < 100
+    return Context(router, context_id, name)
+
+
 class Waker(BasicStream):
     """
     :py:class:`BasicStream` subclass implementing the
diff --git a/mitogen/master.py b/mitogen/master.py
index 5d8e18d9..f9e3341d 100644
--- a/mitogen/master.py
+++ b/mitogen/master.py
@@ -38,11 +38,6 @@ DOCSTRING_RE = re.compile(r'""".+?"""', re.M | re.S)
 COMMENT_RE = re.compile(r'^[ ]*#[^\n]*$', re.M)
 IOLOG_RE = re.compile(r'^[ ]*IOLOG.debug\(.+?\)$', re.M)
 
-PERMITTED_CLASSES = set([
-    ('mitogen.core', '_unpickle_call_error'),
-    ('mitogen.core', '_unpickle_dead'),
-])
-
 
 def minimize_source(source):
     """Remove comments and docstrings from Python `source`, preserving line
@@ -316,27 +311,10 @@ class ModuleForwarder(object):
         )
 
 
-class Message(mitogen.core.Message):
-    """
-    Message subclass that controls unpickling.
-    """
-    def _find_global(self, module_name, class_name):
-        """Return the class implementing `module_name.class_name` or raise
-        `StreamError` if the module is not whitelisted."""
-        if (module_name, class_name) not in PERMITTED_CLASSES:
-            raise mitogen.core.StreamError(
-                'attempted to unpickle %r in module %r',
-                class_name, module_name
-            )
-        return getattr(sys.modules[module_name], class_name)
-
-
 class Stream(mitogen.core.Stream):
     """
     Base for streams capable of starting new slaves.
     """
-    message_class = Message
-
     #: The path to the remote Python interpreter.
     python_path = 'python2.7'
 
diff --git a/tests/call_function_test.py b/tests/call_function_test.py
index 7c63dd70..9cbfe23e 100644
--- a/tests/call_function_test.py
+++ b/tests/call_function_test.py
@@ -20,6 +20,10 @@ def func_returns_dead():
     return mitogen.core._DEAD
 
 
+def func_accepts_returns_context(context):
+    return context
+
+
 class CallFunctionTest(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
@@ -59,8 +63,7 @@ class CallFunctionTest(unittest.TestCase):
             pass
 
         assert e[0] == (
-            "attempted to unpickle 'CrazyType' "
-            "in module 'call_function_test'"
+            "attempted unpickle from 'call_function_test'"
         )
 
     def test_returns_dead(self):
@@ -75,3 +78,9 @@ class CallFunctionTest(unittest.TestCase):
 
     def test_aborted_on_local_broker_shutdown(self):
         assert 0, 'todo'
+
+    def test_accepts_returns_context(self):
+        context = self.local.call(func_accepts_returns_context, self.local)
+        assert context is not self.local
+        assert context.context_id == self.local.context_id
+        assert context.name == self.local.name