diff --git a/IPython/utils/tests/test_traitlets.py b/IPython/utils/tests/test_traitlets.py
index a4a5423..6ec3255 100644
--- a/IPython/utils/tests/test_traitlets.py
+++ b/IPython/utils/tests/test_traitlets.py
@@ -16,7 +16,7 @@ import nose.tools as nt
 from nose import SkipTest
 
 from IPython.utils.traitlets import (
-    HasTraits, MetaHasTraits, TraitType, Any, CBytes, Dict,
+    HasTraits, MetaHasTraits, TraitType, AllowNone, Any, CBytes, Dict,
     Int, Long, Integer, Float, Complex, Bytes, Unicode, TraitError,
     Undefined, Type, This, Instance, TCPAddress, List, Tuple,
     ObjectName, DottedObjectName, CRegExp, link
@@ -73,7 +73,7 @@ class TestTraitType(TestCase):
         self.assertEqual(a.tt, -1)
 
     def test_default_validate(self):
-        class MyIntTT(TraitType):
+        class MyIntTT(AllowNone):
             def validate(self, obj, value):
                 if isinstance(value, int):
                     return value
@@ -354,29 +354,29 @@ class TestHasTraitsNotify(TestCase):
 
         class A(HasTraits):
             listen_to = ['a']
-            
+
             a = Int(0)
             b = 0
-            
+
             def __init__(self, **kwargs):
                 super(A, self).__init__(**kwargs)
                 self.on_trait_change(self.listener1, ['a'])
-            
+
             def listener1(self, name, old, new):
                 self.b += 1
 
         class B(A):
-                    
+
             c = 0
             d = 0
-            
+
             def __init__(self, **kwargs):
                 super(B, self).__init__(**kwargs)
                 self.on_trait_change(self.listener2)
-            
+
             def listener2(self, name, old, new):
                 self.c += 1
-            
+
             def _a_changed(self, name, old, new):
                 self.d += 1
 
@@ -442,7 +442,7 @@ class TestHasTraits(TestCase):
             def __init__(self, i):
                 super(A, self).__init__()
                 self.i = i
-        
+
         a = A(5)
         self.assertEqual(a.i, 5)
         # should raise TypeError if no positional arg given
@@ -673,6 +673,23 @@ class TraitTestBase(TestCase):
         if hasattr(self, '_default_value'):
             self.assertEqual(self._default_value, self.obj.value)
 
+    def test_allow_none(self):
+        if (hasattr(self, '_bad_values') and hasattr(self, '_good_values') and
+        None in self._bad_values):
+            trait=self.obj.traits()['value']
+            if isinstance(trait, AllowNone) and not trait._allow_none:
+                trait._allow_none = True
+                self._bad_values.remove(None)
+                #skip coerce. Allow None casts None to None.
+                self.assign(None)
+                self.assertEqual(self.obj.value,None)
+                self.test_good_values()
+                self.test_bad_values()
+                #tear down
+                trait._allow_none = False
+                self._bad_values.append(None)
+
+
     def tearDown(self):
         # restore default value after tests, if set
         if hasattr(self, '_default_value'):
@@ -830,7 +847,7 @@ class TestObjectName(TraitTestBase):
     _default_value = "abc"
     _good_values = ["a", "gh", "g9", "g_", "_G", u"a345_"]
     _bad_values = [1, "", u"€", "9g", "!", "#abc", "aj@", "a.b", "a()", "a[0]",
-                                                            object(), object]
+                                                        None, object(), object]
     if sys.version_info[0] < 3:
         _bad_values.append(u"þ")
     else:
@@ -845,7 +862,7 @@ class TestDottedObjectName(TraitTestBase):
 
     _default_value = "a.b"
     _good_values = ["A", "y.t", "y765.__repr__", "os.path.join", u"os.path.join"]
-    _bad_values = [1, u"abc.€", "_.@", ".", ".abc", "abc.", ".abc."]
+    _bad_values = [1, u"abc.€", "_.@", ".", ".abc", "abc.", ".abc.", None]
     if sys.version_info[0] < 3:
         _bad_values.append(u"t.þ")
     else:
@@ -862,7 +879,7 @@ class TestTCPAddress(TraitTestBase):
 
     _default_value = ('127.0.0.1',0)
     _good_values = [('localhost',0),('192.168.0.1',1000),('www.google.com',80)]
-    _bad_values = [(0,0),('localhost',10.0),('localhost',-1)]
+    _bad_values = [(0,0),('localhost',10.0),('localhost',-1), None]
 
 class ListTrait(HasTraits):
 
@@ -875,7 +892,7 @@ class TestList(TraitTestBase):
     _default_value = []
     _good_values = [[], [1], list(range(10)), (1,2)]
     _bad_values = [10, [1,'a'], 'a']
-    
+
     def coerce(self, value):
         if value is not None:
             value = list(value)
@@ -1054,7 +1071,7 @@ class TestLink(TestCase):
             count = Int()
         a = A(value=9)
         b = B(count=8)
-        
+
         # Register callbacks that count.
         callback_count = []
         def a_callback(name, old, new):