diff --git a/IPython/core/application.py b/IPython/core/application.py
index f2d4aaf..3a23676 100644
--- a/IPython/core/application.py
+++ b/IPython/core/application.py
@@ -107,7 +107,7 @@ class BaseIPythonApplication(Application):
         os.path.join(get_ipython_package_dir(), u'config', u'profile', u'default')
     )
     
-    config_file_paths = List(Unicode)
+    config_file_paths = List(Unicode())
     def _config_file_paths_default(self):
         return [py3compat.getcwd()]
 
@@ -161,7 +161,7 @@ class BaseIPythonApplication(Application):
     auto_create = Bool(False, config=True,
         help="""Whether to create profile dir if it doesn't exist""")
 
-    config_files = List(Unicode)
+    config_files = List(Unicode())
     def _config_files_default(self):
         return [self.config_file_name]
 
diff --git a/IPython/core/display_trap.py b/IPython/core/display_trap.py
index 93f5a9b..9931dfe 100644
--- a/IPython/core/display_trap.py
+++ b/IPython/core/display_trap.py
@@ -36,7 +36,7 @@ class DisplayTrap(Configurable):
     (no callbacks or formatters) until more of the core is refactored.
     """
 
-    hook = Any
+    hook = Any()
 
     def __init__(self, hook=None):
         super(DisplayTrap, self).__init__(hook=hook, config=None)
diff --git a/IPython/core/formatters.py b/IPython/core/formatters.py
index 07ba159..3a7d598 100644
--- a/IPython/core/formatters.py
+++ b/IPython/core/formatters.py
@@ -70,7 +70,7 @@ class DisplayFormatter(Configurable):
         else:
             self.active_types = self.format_types
     
-    active_types = List(Unicode, config=True,
+    active_types = List(Unicode(), config=True,
         help="""List of currently active mime-types to display.
         You can use this to set a white-list for formats to display.
         
diff --git a/IPython/core/magic.py b/IPython/core/magic.py
index 977b1c4..c44d883 100644
--- a/IPython/core/magic.py
+++ b/IPython/core/magic.py
@@ -296,10 +296,10 @@ class MagicsManager(Configurable):
     # A two-level dict, first keyed by magic type, then by magic function, and
     # holding the actual callable object as value.  This is the dict used for
     # magic function dispatch
-    magics = Dict
+    magics = Dict()
 
     # A registry of the original objects that we've been given holding magics.
-    registry = Dict
+    registry = Dict()
 
     shell = Instance('IPython.core.interactiveshell.InteractiveShellABC', allow_none=True)
 
diff --git a/IPython/core/shellapp.py b/IPython/core/shellapp.py
index ae8ff08..4758c8d 100644
--- a/IPython/core/shellapp.py
+++ b/IPython/core/shellapp.py
@@ -133,7 +133,7 @@ class InteractiveShellApp(Configurable):
       - :meth:`init_extensions`
       - :meth:`init_code`
     """
-    extensions = List(Unicode, config=True,
+    extensions = List(Unicode(), config=True,
         help="A list of dotted module names of IPython extensions to load."
     )
     extra_extension = Unicode('', config=True,
@@ -147,14 +147,14 @@ class InteractiveShellApp(Configurable):
     )
 
     # Extensions that are always loaded (not configurable)
-    default_extensions = List(Unicode, [u'storemagic'], config=False)
+    default_extensions = List(Unicode(), [u'storemagic'], config=False)
     
     hide_initial_ns = Bool(True, config=True,
         help="""Should variables loaded at startup (by startup files, exec_lines, etc.)
         be hidden from tools like %who?"""
     )
 
-    exec_files = List(Unicode, config=True,
+    exec_files = List(Unicode(), config=True,
         help="""List of files to run at IPython startup."""
     )
     exec_PYTHONSTARTUP = Bool(True, config=True,
@@ -164,7 +164,7 @@ class InteractiveShellApp(Configurable):
     file_to_run = Unicode('', config=True,
         help="""A file to be run""")
 
-    exec_lines = List(Unicode, config=True,
+    exec_lines = List(Unicode(), config=True,
         help="""lines of code to run at IPython startup."""
     )
     code_to_run = Unicode('', config=True,