diff --git a/django/core/servers/basehttp.py b/django/core/servers/basehttp.py
index 2db4e5ef6a..ce1558a924 100644
--- a/django/core/servers/basehttp.py
+++ b/django/core/servers/basehttp.py
@@ -7,6 +7,8 @@ This is a simple server for use in testing or debugging Django apps. It hasn't
 been reviewed for security issues. DON'T USE IT FOR PRODUCTION USE!
 """
 
+from __future__ import unicode_literals
+
 import os
 import socket
 import sys
@@ -71,12 +73,12 @@ class WSGIServerException(Exception):
 
 
 class ServerHandler(simple_server.ServerHandler, object):
-    error_status = "500 INTERNAL SERVER ERROR"
+    error_status = str("500 INTERNAL SERVER ERROR")
 
     def write(self, data):
-        """'write()' callable as specified by PEP 333"""
+        """'write()' callable as specified by PEP 3333"""
 
-        assert isinstance(data, str), "write() argument must be string"
+        assert isinstance(data, bytes), "write() argument must be bytestring"
 
         if not self.status:
             raise AssertionError("write() before start_response()")
diff --git a/tests/regressiontests/builtin_server/tests.py b/tests/regressiontests/builtin_server/tests.py
index 4a3b44176b..c8dc77e42e 100644
--- a/tests/regressiontests/builtin_server/tests.py
+++ b/tests/regressiontests/builtin_server/tests.py
@@ -1,5 +1,8 @@
+from __future__ import unicode_literals
+
+from io import BytesIO
+
 from django.core.servers.basehttp import ServerHandler
-from django.utils.six import StringIO
 from django.utils.unittest import TestCase
 
 #
@@ -23,12 +26,12 @@ class FileWrapperHandler(ServerHandler):
         return True
 
 def wsgi_app(environ, start_response):
-    start_response('200 OK', [('Content-Type', 'text/plain')])
-    return ['Hello World!']
+    start_response(str('200 OK'), [(str('Content-Type'), str('text/plain'))])
+    return [b'Hello World!']
 
 def wsgi_app_file_wrapper(environ, start_response):
-    start_response('200 OK', [('Content-Type', 'text/plain')])
-    return environ['wsgi.file_wrapper'](StringIO('foo'))
+    start_response(str('200 OK'), [(str('Content-Type'), str('text/plain'))])
+    return environ['wsgi.file_wrapper'](BytesIO(b'foo'))
 
 class WSGIFileWrapperTests(TestCase):
     """
@@ -37,15 +40,16 @@ class WSGIFileWrapperTests(TestCase):
 
     def test_file_wrapper_uses_sendfile(self):
         env = {'SERVER_PROTOCOL': 'HTTP/1.0'}
-        err = StringIO()
-        handler = FileWrapperHandler(None, StringIO(), err, env)
+        handler = FileWrapperHandler(None, BytesIO(), BytesIO(), env)
         handler.run(wsgi_app_file_wrapper)
         self.assertTrue(handler._used_sendfile)
+        self.assertEqual(handler.stdout.getvalue(), b'')
+        self.assertEqual(handler.stderr.getvalue(), b'')
 
     def test_file_wrapper_no_sendfile(self):
         env = {'SERVER_PROTOCOL': 'HTTP/1.0'}
-        err = StringIO()
-        handler = FileWrapperHandler(None, StringIO(), err, env)
+        handler = FileWrapperHandler(None, BytesIO(), BytesIO(), env)
         handler.run(wsgi_app)
         self.assertFalse(handler._used_sendfile)
-        self.assertEqual(handler.stdout.getvalue().splitlines()[-1],'Hello World!')
+        self.assertEqual(handler.stdout.getvalue().splitlines()[-1], b'Hello World!')
+        self.assertEqual(handler.stderr.getvalue(), b'')