diff --git a/util/queue.py b/util/queue.py
index 9765658..9e4f39d 100644
--- a/util/queue.py
+++ b/util/queue.py
@@ -18,8 +18,10 @@
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 
 
+import sys
 import multiprocessing
 import multiprocessing.queues
+from collections import namedtuple
 
 
 class SharedCounter(object):
@@ -51,6 +53,9 @@ def value(self):
         return self.count.value
 
 
+QueueState = namedtuple('QueueState', ['queue', 'size'])
+
+
 class Queue(multiprocessing.queues.Queue):
     """ A portable implementation of multiprocessing.Queue.
 
@@ -66,9 +71,20 @@ class Queue(multiprocessing.queues.Queue):
     """
 
     def __init__(self, *args, **kwargs):
+        if sys.version_info >= (3, 4) and 'ctx' not in kwargs:
+            kwargs['ctx'] = multiprocessing.get_context()
         super(Queue, self).__init__(*args, **kwargs)
         self._size = SharedCounter(0)
 
+    # __getstate__ and __setstate__ are needed for pickling, otherwise _size won't be copied.
+    def __getstate__(self):
+        return QueueState(queue=super(Queue, self).__getstate__(),
+                          size=self._size)
+
+    def __setstate__(self, state):
+        self._size = state.size
+        super(Queue, self).__setstate__(state.queue)
+
     def put(self, *args, **kwargs):
         super(Queue, self).put(*args, **kwargs)
         self._size.increment(1)