diff --git a/src/structures.py b/src/structures.py
index dd0e622a9..8c6f05c98 100644
--- a/src/structures.py
+++ b/src/structures.py
@@ -321,6 +321,10 @@ class MaxLengthQueue(queue):
 class TwoWayDictionary(dict):
     __slots__ = ()
     def __init__(self, seq=(), **kwargs):
+        if hasattr(seq, 'iteritems'):
+            seq = seq.iteritems()
+        elif hasattr(seq, 'items'):
+            seq = seq.items()
         for (key, value) in seq:
             self[key] = value
             self[value] = key
diff --git a/test/test_structures.py b/test/test_structures.py
index 497867f59..ad92ee81d 100644
--- a/test/test_structures.py
+++ b/test/test_structures.py
@@ -555,6 +555,10 @@ class TwoWayDictionaryTestCase(unittest.TestCase):
         self.failUnless('foo' in d)
         self.failUnless('bar' in d)
 
+        d = TwoWayDictionary({1: 2})
+        self.failUnless(1 in d)
+        self.failUnless(2 in d)
+
     def testSetitem(self):
         d = TwoWayDictionary()
         d['foo'] = 'bar'