diff --git a/IPython/config/application.py b/IPython/config/application.py
index 0ca2d02..bb05472 100644
--- a/IPython/config/application.py
+++ b/IPython/config/application.py
@@ -174,7 +174,7 @@ class Application(SingletonConfigurable):
         _log_handler.setFormatter(_log_formatter)
     
 
-    log = Instance(logging.Logger, allow_none=True)
+    log = Instance(logging.Logger)
     def _log_default(self):
         """Start logging for this application.
 
diff --git a/IPython/config/configurable.py b/IPython/config/configurable.py
index 0f95b04..d1a8e68 100644
--- a/IPython/config/configurable.py
+++ b/IPython/config/configurable.py
@@ -372,7 +372,7 @@ class LoggingConfigurable(Configurable):
     is to get the logger from the currently running Application.
     """
 
-    log = Instance('logging.Logger', allow_none=True)
+    log = Instance('logging.Logger')
     def _log_default(self):
         from IPython.utils import log
         return log.get_logger()
diff --git a/IPython/core/interactiveshell.py b/IPython/core/interactiveshell.py
index dc77e77..18bc703 100644
--- a/IPython/core/interactiveshell.py
+++ b/IPython/core/interactiveshell.py
@@ -301,7 +301,7 @@ class InteractiveShell(SingletonConfigurable):
     data_pub_class = None
 
     exit_now = CBool(False)
-    exiter = Instance(ExitAutocall, allow_none=True)
+    exiter = Instance(ExitAutocall)
     def _exiter_default(self):
         return ExitAutocall(self)
     # Monotonically increasing execution counter
@@ -453,7 +453,7 @@ class InteractiveShell(SingletonConfigurable):
 
 
     # Private interface
-    _post_execute = Instance(dict, allow_none=True)
+    _post_execute = Dict()
 
     # Tracks any GUI loop loaded for pylab
     pylab_gui_select = None
diff --git a/IPython/html/services/clusters/clustermanager.py b/IPython/html/services/clusters/clustermanager.py
index f428273..c0a8776 100644
--- a/IPython/html/services/clusters/clustermanager.py
+++ b/IPython/html/services/clusters/clustermanager.py
@@ -20,7 +20,7 @@ class ClusterManager(LoggingConfigurable):
     delay = Float(1., config=True,
         help="delay (in s) between starting the controller and the engines")
 
-    loop = Instance('zmq.eventloop.ioloop.IOLoop', allow_none=True)
+    loop = Instance('zmq.eventloop.ioloop.IOLoop')
     def _loop_default(self):
         from zmq.eventloop.ioloop import IOLoop
         return IOLoop.instance()
diff --git a/IPython/kernel/zmq/zmqshell.py b/IPython/kernel/zmq/zmqshell.py
index 6c2f948..c933f07 100644
--- a/IPython/kernel/zmq/zmqshell.py
+++ b/IPython/kernel/zmq/zmqshell.py
@@ -367,7 +367,7 @@ class ZMQInteractiveShell(InteractiveShell):
     # will print a warning in the absence of readline.
     autoindent = CBool(False)
 
-    exiter = Instance(ZMQExitAutocall, allow_none=True)
+    exiter = Instance(ZMQExitAutocall)
     def _exiter_default(self):
         return ZMQExitAutocall(self)
     
diff --git a/ipython_parallel/apps/baseapp.py b/ipython_parallel/apps/baseapp.py
index c78cb08..15aa84e 100644
--- a/ipython_parallel/apps/baseapp.py
+++ b/ipython_parallel/apps/baseapp.py
@@ -123,7 +123,7 @@ class BaseParallelApplication(BaseIPythonApplication):
     def _config_files_default(self):
         return ['ipcontroller_config.py', 'ipengine_config.py', 'ipcluster_config.py']
     
-    loop = Instance('zmq.eventloop.ioloop.IOLoop', allow_none=True)
+    loop = Instance('zmq.eventloop.ioloop.IOLoop')
     def _loop_default(self):
         from zmq.eventloop.ioloop import IOLoop
         return IOLoop.instance()
diff --git a/ipython_parallel/apps/logwatcher.py b/ipython_parallel/apps/logwatcher.py
index 3b7964a..df9d943 100644
--- a/ipython_parallel/apps/logwatcher.py
+++ b/ipython_parallel/apps/logwatcher.py
@@ -52,7 +52,7 @@ class LogWatcher(LoggingConfigurable):
     # internals
     stream = Instance('zmq.eventloop.zmqstream.ZMQStream', allow_none=True)
     
-    context = Instance(zmq.Context, allow_none=True)
+    context = Instance(zmq.Context)
     def _context_default(self):
         return zmq.Context.instance()
     
diff --git a/ipython_parallel/controller/heartmonitor.py b/ipython_parallel/controller/heartmonitor.py
index 83b076f..aa59fe2 100755
--- a/ipython_parallel/controller/heartmonitor.py
+++ b/ipython_parallel/controller/heartmonitor.py
@@ -79,7 +79,7 @@ class HeartMonitor(LoggingConfigurable):
 
     pingstream=Instance('zmq.eventloop.zmqstream.ZMQStream', allow_none=True)
     pongstream=Instance('zmq.eventloop.zmqstream.ZMQStream', allow_none=True)
-    loop = Instance('zmq.eventloop.ioloop.IOLoop', allow_none=True)
+    loop = Instance('zmq.eventloop.ioloop.IOLoop')
     def _loop_default(self):
         return ioloop.IOLoop.instance()