diff --git a/IPython/utils/tests/test_traitlets.py b/IPython/utils/tests/test_traitlets.py
index a4a5423..2cbd920 100644
--- a/IPython/utils/tests/test_traitlets.py
+++ b/IPython/utils/tests/test_traitlets.py
@@ -881,6 +881,25 @@ class TestList(TraitTestBase):
             value = list(value)
         return value
 
+class Foo(object):
+    pass
+
+class InstanceListTrait(HasTraits):
+
+    value = List(Instance(__name__+'.Foo'))
+
+class TestInstanceList(TraitTestBase):
+
+    obj = InstanceListTrait()
+
+    def test_klass(self):
+        """Test that the instance klass is properly assigned."""
+        self.assertIs(self.obj.traits()['value']._trait.klass, Foo)
+
+    _default_value = []
+    _good_values = [[Foo(), Foo(), None], None]
+    _bad_values = [['1', 2,], '1', [Foo]]
+
 class LenListTrait(HasTraits):
 
     value = List(Int, [0], minlen=1, maxlen=2)
@@ -1105,4 +1124,4 @@ def test_pickle_hastraits():
         c2 = pickle.loads(p)
         nt.assert_equal(c2.i, c.i)
         nt.assert_equal(c2.j, c.j)
-    
\ No newline at end of file
+    
diff --git a/IPython/utils/traitlets.py b/IPython/utils/traitlets.py
index 8141cf6..0cc0c75 100644
--- a/IPython/utils/traitlets.py
+++ b/IPython/utils/traitlets.py
@@ -1297,6 +1297,11 @@ class Container(Instance):
                 validated.append(v)
         return self.klass(validated)
 
+    def instance_init(self, obj):
+        if isinstance(self._trait, Instance):
+            self._trait._resolve_classes()
+        super(Container, self).instance_init(obj)
+
 
 class List(Container):
     """An instance of a Python list."""