Index: Lib/subprocess.py
===================================================================
--- Lib/subprocess.py	(revision 84972)
+++ Lib/subprocess.py	(working copy)
@@ -677,8 +677,6 @@
             if errread != -1:
                 errread = msvcrt.open_osfhandle(errread.Detach(), 0)
 
-        if bufsize == 0:
-            bufsize = 1  # Nearly unbuffered (XXX for now)
         if p2cwrite != -1:
             self.stdin = io.open(p2cwrite, 'wb', bufsize)
             if self.universal_newlines: