diff --git a/python/google/protobuf/internal/reflection_test.py b/python/google/protobuf/internal/reflection_test.py
index b3c414c7..78a880e8 100755
--- a/python/google/protobuf/internal/reflection_test.py
+++ b/python/google/protobuf/internal/reflection_test.py
@@ -1556,7 +1556,6 @@ class ReflectionTest(basetest.TestCase):
 
   def assertNotInitialized(self, proto):
     self.assertFalse(proto.IsInitialized())
-    self.assertRaises(message.EncodeError, proto.SerializeToString)
     # "Partial" serialization doesn't care if message is uninitialized.
     proto.SerializePartialToString()
 
@@ -2491,11 +2490,6 @@ class SerializationTest(basetest.TestCase):
 
   def testSerializeUninitialized(self):
     proto = unittest_pb2.TestRequired()
-    self._CheckRaises(
-        message.EncodeError,
-        proto.SerializeToString,
-        'Message protobuf_unittest.TestRequired is missing required fields: '
-        'a,b,c')
     # Shouldn't raise exceptions.
     partial = proto.SerializePartialToString()
 
@@ -2506,18 +2500,10 @@ class SerializationTest(basetest.TestCase):
     self.assertFalse(proto2.HasField('a'))
 
     proto.a = 1
-    self._CheckRaises(
-        message.EncodeError,
-        proto.SerializeToString,
-        'Message protobuf_unittest.TestRequired is missing required fields: b,c')
     # Shouldn't raise exceptions.
     partial = proto.SerializePartialToString()
 
     proto.b = 2
-    self._CheckRaises(
-        message.EncodeError,
-        proto.SerializeToString,
-        'Message protobuf_unittest.TestRequired is missing required fields: c')
     # Shouldn't raise exceptions.
     partial = proto.SerializePartialToString()
 
@@ -2547,12 +2533,6 @@ class SerializationTest(basetest.TestCase):
     proto.SerializeToString()
 
     proto.optional_message.a = 1
-    self._CheckRaises(
-        message.EncodeError,
-        proto.SerializeToString,
-        'Message protobuf_unittest.TestRequiredForeign '
-        'is missing required fields: '
-        'optional_message.b,optional_message.c')
 
     proto.optional_message.b = 2
     proto.optional_message.c = 3
@@ -2560,12 +2540,6 @@ class SerializationTest(basetest.TestCase):
 
     proto.repeated_message.add().a = 1
     proto.repeated_message.add().b = 2
-    self._CheckRaises(
-        message.EncodeError,
-        proto.SerializeToString,
-        'Message protobuf_unittest.TestRequiredForeign is missing required fields: '
-        'repeated_message[0].b,repeated_message[0].c,'
-        'repeated_message[1].a,repeated_message[1].c')
 
     proto.repeated_message[0].b = 2
     proto.repeated_message[0].c = 3
diff --git a/python/google/protobuf/internal/descriptor_cpp2_test.py b/python/google/protobuf/pyext/descriptor_cpp2_test.py
similarity index 100%
rename from python/google/protobuf/internal/descriptor_cpp2_test.py
rename to python/google/protobuf/pyext/descriptor_cpp2_test.py
diff --git a/python/google/protobuf/internal/message_factory_cpp2_test.py b/python/google/protobuf/pyext/message_factory_cpp2_test.py
similarity index 100%
rename from python/google/protobuf/internal/message_factory_cpp2_test.py
rename to python/google/protobuf/pyext/message_factory_cpp2_test.py
diff --git a/python/google/protobuf/internal/reflection_cpp2_generated_test.py b/python/google/protobuf/pyext/reflection_cpp2_generated_test.py
similarity index 100%
rename from python/google/protobuf/internal/reflection_cpp2_generated_test.py
rename to python/google/protobuf/pyext/reflection_cpp2_generated_test.py
diff --git a/python/setup.py b/python/setup.py
index db3a32e9..51b27d72 100755
--- a/python/setup.py
+++ b/python/setup.py
@@ -122,12 +122,10 @@ class build_py(_build_py):
 
 if __name__ == '__main__':
   # C++ implementation extension
-  nocpp = '--nocpp_implementation'
-  if nocpp in sys.argv:
-    ext_module_list = []
-    sys.argv.remove(nocpp)
-  else:
-    nocpp = False
+  cpp_impl = '--cpp_implementation'
+  if cpp_impl in sys.argv:
+    sys.argv.remove(cpp_impl)
+    test_dir = "google/protobuf/pyext"
     ext_module_list = [Extension(
         "google.protobuf.pyext._message",
         [ "google/protobuf/pyext/descriptor.cc",
@@ -140,12 +138,16 @@ if __name__ == '__main__':
         libraries = [ "protobuf" ],
         library_dirs = [ '../src/.libs' ],
         )]
+  else:
+    test_dir = "google/protobuf/internal"
+    ext_module_list = []
+
 
   setup(name = 'protobuf',
         version = '2.6-pre',
         packages = [ 'google' ],
         namespace_packages = [ 'google' ],
-        google_test_dir = "google/protobuf/internal",
+        google_test_dir = test_dir,
         # Must list modules explicitly so that we don't install tests.
         py_modules = [
           'google.protobuf.internal.api_implementation',
@@ -182,5 +184,4 @@ if __name__ == '__main__':
         description = 'Protocol Buffers',
         long_description =
           "Protocol Buffers are Google's data interchange format.",
-        use_2to3=True,
         )