diff --git a/IPython/frontend/prefilterfrontend.py b/IPython/frontend/prefilterfrontend.py
index f1b941c..8479132 100644
--- a/IPython/frontend/prefilterfrontend.py
+++ b/IPython/frontend/prefilterfrontend.py
@@ -92,8 +92,10 @@ This is the wx frontend, by Gael Varoquaux. This is EXPERIMENTAL code."""
 
         LineFrontEndBase.__init__(self, *args, **kwargs)
         # XXX: Hack: mix the two namespaces
-        self.shell.user_ns = self.ipython0.user_ns
-        self.shell.user_global_ns = self.ipython0.user_global_ns
+        self.shell.user_ns.update(self.ipython0.user_ns)
+        self.ipython0.user_ns = self.shell.user_ns 
+        self.shell.user_global_ns.update(self.ipython0.user_global_ns)
+        self.ipython0.user_global_ns = self.shell.user_global_ns
 
         self.shell.output_trap = RedirectorOutputTrap(
                             out_callback=self.write,
diff --git a/IPython/frontend/tests/test_prefilterfrontend.py b/IPython/frontend/tests/test_prefilterfrontend.py
index f786170..665a2c5 100644
--- a/IPython/frontend/tests/test_prefilterfrontend.py
+++ b/IPython/frontend/tests/test_prefilterfrontend.py
@@ -17,6 +17,7 @@ import string
 
 from IPython.ipapi import get as get_ipython0
 from IPython.frontend.prefilterfrontend import PrefilterFrontEnd
+from copy import deepcopy
 
 class TestPrefilterFrontEnd(PrefilterFrontEnd):
     
@@ -49,6 +50,23 @@ class TestPrefilterFrontEnd(PrefilterFrontEnd):
         PrefilterFrontEnd._on_enter(self)
 
 
+def isolate_ipython0(func):
+    """ Decorator to isolate execution that involves an iptyhon0.
+    """
+    def my_func(*args, **kwargs):
+        ipython0 = get_ipython0().IP
+        user_ns = deepcopy(ipython0.user_ns)
+        global_ns = deepcopy(ipython0.global_ns)
+        try:
+            func(*args, **kwargs)
+        finally:
+            ipython0.user_ns = user_ns
+            ipython0.global_ns = global_ns
+
+    return my_func
+
+
+@isolate_ipython0
 def test_execution():
     """ Test execution of a command.
     """
@@ -59,6 +77,7 @@ def test_execution():
     assert out_value  == '1\n'
 
 
+@isolate_ipython0
 def test_multiline():
     """ Test execution of a multiline command.
     """
@@ -84,6 +103,7 @@ def test_multiline():
     assert out_value == '1\n'
 
 
+@isolate_ipython0
 def test_capture():
     """ Test the capture of output in different channels.
     """
@@ -102,6 +122,7 @@ def test_capture():
     assert out_value == '1'
 
      
+@isolate_ipython0
 def test_magic():
     """ Test the magic expansion and history.
     
@@ -114,6 +135,7 @@ def test_magic():
     assert out_value == 'Interactive namespace is empty.\n'
 
 
+@isolate_ipython0
 def test_help():
     """ Test object inspection.
     """
@@ -133,6 +155,7 @@ def test_help():
     #assert out_value.split()[-1] == 'foobar' 
 
 
+@isolate_ipython0
 def test_completion():
     """ Test command-line completion.
     """