diff --git a/sipsimple/addressbook.py b/sipsimple/addressbook.py
index f57c1fc25..fbc3c38ce 100644
--- a/sipsimple/addressbook.py
+++ b/sipsimple/addressbook.py
@@ -19,7 +19,7 @@
 from application.python import Null
 from application.python.decorator import execute_once
 from application.python.types import Singleton, MarkerType
-from application.python.weakref import weakobjectmap
+from application.python.weakref import defaultweakobjectmap
 
 from sipsimple.account import xcap, AccountManager
 from sipsimple.configuration import ConfigurationManager, ObjectNotFoundError, DuplicateIDError, PersistentKey, ModifiedValue, ModifiedList
@@ -50,14 +50,6 @@ def __repr__(self):
         return "%s(%r, %r)" % (self.__class__.__name__, self.account, self.xcap_object)
 
 
-class defaultweakobjectmap(weakobjectmap):
-    def __init__(self, factory, *args, **kw):
-        self.default_factory = factory
-        super(defaultweakobjectmap, self).__init__(*args, **kw)
-    def __missing__(self, key):
-        return self.setdefault(key.object, self.default_factory())
-
-
 class Setting(AbstractSetting):
     """
     Descriptor represeting a setting in an addressbook object.