diff -r dcf9e9ae5393 Lib/test/test_ordered_dict.py
--- a/Lib/test/test_ordered_dict.py	Wed Dec 23 00:37:50 2015 +0200
+++ b/Lib/test/test_ordered_dict.py	Wed Dec 23 16:10:04 2015 +0200
@@ -546,7 +546,7 @@ class OrderedDictTests:
         dict.__setitem__(od, 'spam', 1)
         self.assertNotIn('NULL', repr(od))
 
-    def test_dict_delitem(self):
+    def test_dict_delitem_repr(self):
         OrderedDict = self.OrderedDict
         od = OrderedDict()
         od['spam'] = 1
@@ -555,6 +555,45 @@ class OrderedDictTests:
         with self.assertRaises(KeyError):
             repr(od)
 
+    def test_dict_delitem_iter(self):
+        OrderedDict = self.OrderedDict
+        keys = ['key%s' % i for i in range(10)]
+        od = OrderedDict()
+        for k in keys:
+            od[k] = k
+        for k in keys[:-1]:
+            dict.__delitem__(od, k)
+
+        it = iter(od.items())
+        with self.assertRaises(KeyError):
+            next(it)
+        it = iter(od.values())
+        with self.assertRaises(KeyError):
+            next(it)
+        it = iter(od)
+        try:
+            # Shouldn't hung
+            list(it)
+        except KeyError:
+            # C implementation raises an error, Python implementation doesn't
+            pass
+
+    def test_dict_delitem_move_to_end(self):
+        OrderedDict = self.OrderedDict
+        keys = ['key%s' % i for i in range(10)]
+        od = OrderedDict()
+        for k in keys:
+            od[k] = k
+        for k in keys[1:]:
+            dict.__delitem__(od, k)
+
+        od.move_to_end(keys[0])
+        try:
+            od.move_to_end(keys[1])
+        except KeyError:
+            # C implementation raises an error, Python implementation doesn't
+            pass
+
     def test_dict_clear(self):
         OrderedDict = self.OrderedDict
         od = OrderedDict()
diff -r dcf9e9ae5393 Objects/odictobject.c
--- a/Objects/odictobject.c	Wed Dec 23 00:37:50 2015 +0200
+++ b/Objects/odictobject.c	Wed Dec 23 16:10:04 2015 +0200
@@ -620,6 +620,7 @@ static _ODictNode *
 {
     Py_ssize_t index;
     Py_hash_t hash;
+    _ODictNode *node;
 
     if (_odict_EMPTY(od))
         return NULL;
@@ -629,7 +630,12 @@ static _ODictNode *
     index = _odict_get_index(od, key, hash);
     if (index < 0)
         return NULL;
-    return od->od_fast_nodes[index];
+    node = od->od_fast_nodes[index];
+    if (node == NULL)
+        return NULL;
+    if (node->key != od->od_dict.ma_keys->dk_entries[index].me_key)
+        return NULL;
+    return node;
 }
 
 static void
@@ -1023,7 +1029,6 @@ odict_setdefault(register PyODictObject 
         if (result == NULL) {
             if (PyErr_Occurred())
                 return NULL;
-            assert(_odict_find_node(od, key) == NULL);
             if (PyODict_SetItem((PyObject *)od, key, failobj) >= 0) {
                 result = failobj;
                 Py_INCREF(failobj);