diff --git a/mitogen/core.py b/mitogen/core.py
index 4b3df595..607c4bfb 100644
--- a/mitogen/core.py
+++ b/mitogen/core.py
@@ -2840,7 +2840,7 @@ class Broker(object):
     #: before force-disconnecting them during :meth:`shutdown`.
     shutdown_timeout = 3.0
 
-    def __init__(self, poller_class=None):
+    def __init__(self, poller_class=None, activate_compat=True):
         self._alive = True
         self._exitted = False
         self._waker = Waker(self)
@@ -2858,6 +2858,19 @@ class Broker(object):
             name='mitogen.broker'
         )
         self._thread.start()
+        if activate_compat:
+            self._py24_25_compat()
+
+    def _py24_25_compat(self):
+        """
+        Python 2.4/2.5 have grave difficulties with threads/fork. We
+        mandatorily quiesce all running threads during fork using a
+        monkey-patch there.
+        """
+        if sys.version_info < (2, 6):
+            # import_module() is used to avoid dep scanner.
+            os_fork = import_module('mitogen.os_fork')
+            mitogen.os_fork._notice_broker_or_pool(self)
 
     def start_receive(self, stream):
         """
@@ -3003,6 +3016,7 @@ class Broker(object):
         except Exception:
             LOG.exception('_broker_main() crashed')
 
+        self._alive = False  # Ensure _alive is consistent on crash.
         self._exitted = True
         self._broker_exit()
 
@@ -3206,7 +3220,7 @@ class ExternalContext(object):
         Router.max_message_size = self.config['max_message_size']
         if self.config['profiling']:
             enable_profiling()
-        self.broker = Broker()
+        self.broker = Broker(activate_compat=False)
         self.router = Router(self.broker)
         self.router.debug = self.config.get('debug', False)
         self.router.undirectional = self.config['unidirectional']
@@ -3348,17 +3362,6 @@ class ExternalContext(object):
         # Reopen with line buffering.
         sys.stdout = os.fdopen(1, 'w', 1)
 
-    def _py24_25_compat(self):
-        """
-        Python 2.4/2.5 have grave difficulties with threads/fork. We
-        mandatorily quiesce all running threads during fork using a
-        monkey-patch there.
-        """
-        if sys.version_info < (2, 6):
-            # import_module() is used to avoid dep scanner.
-            os_fork = import_module('mitogen.os_fork')
-            mitogen.os_fork._notice_broker_or_pool(self.broker)
-
     def main(self):
         self._setup_master()
         try:
@@ -3386,7 +3389,7 @@ class ExternalContext(object):
                                  socket.gethostname())
                 _v and LOG.debug('Recovered sys.executable: %r', sys.executable)
 
-                self._py24_25_compat()
+                self.broker._py24_25_compat()
                 self.dispatcher.run()
                 _v and LOG.debug('ExternalContext.main() normal exit')
             except KeyboardInterrupt:
diff --git a/mitogen/os_fork.py b/mitogen/os_fork.py
index 2b74bdfc..e6a3aafc 100644
--- a/mitogen/os_fork.py
+++ b/mitogen/os_fork.py
@@ -48,21 +48,21 @@ import mitogen.core
 
 # List of weakrefs. On Python 2.4, mitogen.core registers its Broker on this
 # list and mitogen.service registers its Pool too.
-_brokers = weakref.WeakValueDictionary()
-_pools = weakref.WeakValueDictionary()
+_brokers = weakref.WeakKeyDictionary()
+_pools = weakref.WeakKeyDictionary()
 
 
 def _notice_broker_or_pool(obj):
     if isinstance(obj, mitogen.core.Broker):
-        _brokers[id(obj)] = obj
+        _brokers[obj] = True
     else:
-        _pools[id(obj)] = obj
+        _pools[obj] = True
 
 
 def wrap_os__fork():
     corker = Corker(
-        brokers=list(_brokers.values()),
-        pools=list(_pools.values()),
+        brokers=list(_brokers),
+        pools=list(_pools),
     )
     try:
         corker.cork()
diff --git a/tests/router_test.py b/tests/router_test.py
index 4e2c19ed..80169e34 100644
--- a/tests/router_test.py
+++ b/tests/router_test.py
@@ -174,6 +174,8 @@ class CrashTest(testlib.BrokerMixin, testlib.TestCase):
         expect = '_broker_main() crashed'
         self.assertTrue(expect in log.stop())
 
+        self.broker.join()
+
 
 class AddHandlerTest(testlib.TestCase):
     klass = mitogen.master.Router
diff --git a/tests/testlib.py b/tests/testlib.py
index 75061b26..37c3c654 100644
--- a/tests/testlib.py
+++ b/tests/testlib.py
@@ -432,6 +432,7 @@ class BrokerMixin(object):
         if not self.broker_shutdown:
             self.broker.shutdown()
         self.broker.join()
+        del self.broker
         super(BrokerMixin, self).tearDown()
 
     def sync_with_broker(self):
@@ -445,6 +446,10 @@ class RouterMixin(BrokerMixin):
         super(RouterMixin, self).setUp()
         self.router = self.router_class(self.broker)
 
+    def tearDown(self):
+        del self.router
+        super(RouterMixin, self).tearDown()
+
 
 class DockerMixin(RouterMixin):
     @classmethod