Index: core/servers/basehttp.py
===================================================================
--- core/servers/basehttp.py	(revision 6778)
+++ core/servers/basehttp.py	(working copy)
@@ -386,7 +386,7 @@
     def write(self, data):
         """'write()' callable as specified by PEP 333"""
 
-        assert type(data) is StringType,"write() argument must be string"
+        assert isinstance(data, StringType),"write() argument must be string"
 
         if not self.status:
             raise AssertionError("write() before start_response()")