diff --git a/mitogen/core.py b/mitogen/core.py
index 4b8565ca..4b3df595 100644
--- a/mitogen/core.py
+++ b/mitogen/core.py
@@ -3348,6 +3348,17 @@ 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:
@@ -3375,6 +3386,7 @@ class ExternalContext(object):
                                  socket.gethostname())
                 _v and LOG.debug('Recovered sys.executable: %r', sys.executable)
 
+                self._py24_25_compat()
                 self.dispatcher.run()
                 _v and LOG.debug('ExternalContext.main() normal exit')
             except KeyboardInterrupt:
diff --git a/mitogen/service.py b/mitogen/service.py
index 6f50275d..dc200b95 100644
--- a/mitogen/service.py
+++ b/mitogen/service.py
@@ -474,6 +474,7 @@ class Pool(object):
 
         for service in services:
             self.add(service)
+        self._py_24_25_compat()
         self._threads = []
         for x in range(size):
             name = 'mitogen.service.Pool.%x.worker-%d' % (id(self), x,)
@@ -487,6 +488,13 @@ class Pool(object):
 
         LOG.debug('%r: initialized', self)
 
+    def _py_24_25_compat(self):
+        if sys.version_info < (2, 6):
+            # import_module() is used to avoid dep scanner sending mitogen.fork
+            # to all mitogen.service importers.
+            os_fork = mitogen.core.import_module('mitogen.os_fork')
+            os_fork._notice_broker_or_pool(self)
+
     @property
     def size(self):
         return len(self._threads)
diff --git a/tests/responder_test.py b/tests/responder_test.py
index da4f22d7..dbc68a3c 100644
--- a/tests/responder_test.py
+++ b/tests/responder_test.py
@@ -74,8 +74,9 @@ class GoodModulesTest(testlib.RouterMixin, testlib.TestCase):
         context = self.router.local()
 
         self.assertEquals(256, context.call(plain_old_module.pow, 2, 8))
-        self.assertEquals(1, self.router.responder.get_module_count)
-        self.assertEquals(1, self.router.responder.good_load_module_count)
+        os_fork = int(sys.version_info < (2, 6))  # mitogen.os_fork
+        self.assertEquals(1+os_fork, self.router.responder.get_module_count)
+        self.assertEquals(1+os_fork, self.router.responder.good_load_module_count)
         self.assertLess(300, self.router.responder.good_load_module_size)
 
     def test_simple_pkg(self):
@@ -84,8 +85,9 @@ class GoodModulesTest(testlib.RouterMixin, testlib.TestCase):
         context = self.router.local()
         self.assertEquals(3,
             context.call(simple_pkg.a.subtract_one_add_two, 2))
-        self.assertEquals(2, self.router.responder.get_module_count)
-        self.assertEquals(3, self.router.responder.good_load_module_count)
+        os_fork = int(sys.version_info < (2, 6))  # mitogen.os_fork
+        self.assertEquals(2+os_fork, self.router.responder.get_module_count)
+        self.assertEquals(3+os_fork, self.router.responder.good_load_module_count)
         self.assertEquals(0, self.router.responder.bad_load_module_count)
         self.assertLess(450, self.router.responder.good_load_module_size)
 
@@ -185,9 +187,10 @@ class ForwardTest(testlib.RouterMixin, testlib.TestCase):
         c1 = self.router.local()
         c2 = self.router.local(via=c1)
 
+        os_fork = int(sys.version_info < (2, 6))
         self.assertEquals(256, c2.call(plain_old_module.pow, 2, 8))
-        self.assertEquals(2, self.router.responder.get_module_count)
-        self.assertEquals(2, self.router.responder.good_load_module_count)
+        self.assertEquals(2+os_fork, self.router.responder.get_module_count)
+        self.assertEquals(2+os_fork, self.router.responder.good_load_module_count)
         self.assertLess(10000, self.router.responder.good_load_module_size)
         self.assertGreater(40000, self.router.responder.good_load_module_size)