diff --git a/IPython/testing/globalipapp.py b/IPython/testing/globalipapp.py
index 44717ec..82f752c 100644
--- a/IPython/testing/globalipapp.py
+++ b/IPython/testing/globalipapp.py
@@ -84,67 +84,6 @@ def _run_ns_sync(self,arg_s,runner=None):
     return get_ipython().magic_run_ori(arg_s, runner, finder)
 
 
-class ipnsdict(dict):
-    """A special subclass of dict for use as an IPython namespace in doctests.
-
-    This subclass adds a simple checkpointing capability so that when testing
-    machinery clears it (we use it as the test execution context), it doesn't
-    get completely destroyed.
-
-    In addition, it can handle the presence of the '_' key in a special manner,
-    which is needed because of how Python's doctest machinery operates with
-    '_'.  See constructor and :meth:`update` for details.
-    """
-
-    def __init__(self,*a):
-        dict.__init__(self,*a)
-        self._savedict = {}
-        # If this flag is True, the .update() method will unconditionally
-        # remove a key named '_'.  This is so that such a dict can be used as a
-        # namespace in doctests that call '_'.
-        self.protect_underscore = False
-
-    def clear(self):
-        dict.clear(self)
-        self.update(self._savedict)
-
-    def _checkpoint(self):
-        self._savedict.clear()
-        self._savedict.update(self)
-
-    def update(self,other):
-        self._checkpoint()
-        dict.update(self,other)
-
-        if self.protect_underscore:
-            # If '_' is in the namespace, python won't set it when executing
-            # code *in doctests*, and we have multiple doctests that use '_'.
-            # So we ensure that the namespace is always 'clean' of it before
-            # it's used for test code execution.
-            # This flag is only turned on by the doctest machinery, so that
-            # normal test code can assume the _ key is updated like any other
-            # key and can test for its presence after cell executions.
-            self.pop('_', None)
-
-        # The builtins namespace must *always* be the real __builtin__ module,
-        # else weird stuff happens.  The main ipython code does have provisions
-        # to ensure this after %run, but since in this class we do some
-        # aggressive low-level cleaning of the execution namespace, we need to
-        # correct for that ourselves, to ensure consitency with the 'real'
-        # ipython.
-        self['__builtins__'] = builtin_mod
-
-    def __delitem__(self, key):
-        """Part of the test suite checks that we can release all
-        references to an object. So we need to make sure that we're not
-        keeping a reference in _savedict."""
-        dict.__delitem__(self, key)
-        try:
-            del self._savedict[key]
-        except KeyError:
-            pass
-
-
 def get_ipython():
     # This will get replaced by the real thing once we start IPython below
     return start_ipython()
@@ -189,7 +128,6 @@ def start_ipython():
 
     # Create and initialize our test-friendly IPython instance.
     shell = TerminalInteractiveShell.instance(config=config,
-                                              user_ns=ipnsdict(),
                                               )
 
     # A few more tweaks needed for playing nicely with doctests...
diff --git a/IPython/testing/plugin/ipdoctest.py b/IPython/testing/plugin/ipdoctest.py
index 50cc72b..1571e31 100644
--- a/IPython/testing/plugin/ipdoctest.py
+++ b/IPython/testing/plugin/ipdoctest.py
@@ -19,7 +19,7 @@ Limitations:
 # Module imports
 
 # From the standard library
-import __builtin__
+import __builtin__ as builtin_mod
 import commands
 import doctest
 import inspect
@@ -267,18 +267,18 @@ class DocTestCase(doctests.DocTestCase):
     def setUp(self):
         """Modified test setup that syncs with ipython namespace"""
         #print "setUp test", self._dt_test.examples # dbg
-        if isinstance(self._dt_test.examples[0],IPExample):
+        if isinstance(self._dt_test.examples[0], IPExample):
             # for IPython examples *only*, we swap the globals with the ipython
             # namespace, after updating it with the globals (which doctest
             # fills with the necessary info from the module being tested).
             self.user_ns_orig = {}
             self.user_ns_orig.update(_ip.user_ns)
             _ip.user_ns.update(self._dt_test.globs)
+            # We must remove the _ key in the namespace, so that Python's
+            # doctest code sets it naturally
+            _ip.user_ns.pop('_', None)
+            _ip.user_ns['__builtins__'] = builtin_mod
             self._dt_test.globs = _ip.user_ns
-            # IPython must protect the _ key in the namespace (it can't exist)
-            # so that Python's doctest code sets it naturally, so we enable
-            # this feature of our testing namespace.
-            _ip.user_ns.protect_underscore = True
 
         super(DocTestCase, self).setUp()
 
@@ -286,13 +286,10 @@ class DocTestCase(doctests.DocTestCase):
 
         # Undo the test.globs reassignment we made, so that the parent class
         # teardown doesn't destroy the ipython namespace
-        if isinstance(self._dt_test.examples[0],IPExample):
+        if isinstance(self._dt_test.examples[0], IPExample):
             self._dt_test.globs = self._dt_test_globs_ori
             _ip.user_ns.clear()
             _ip.user_ns.update(self.user_ns_orig)
-            # Restore the behavior of the '_' key in the user namespace to
-            # normal after each doctest, so that unittests behave normally
-            _ip.user_ns.protect_underscore = False
 
         # XXX - fperez: I am not sure if this is truly a bug in nose 0.11, but
         # it does look like one to me: its tearDown method tries to run