diff -r 406c6fd7e753 Lib/imaplib.py
--- a/Lib/imaplib.py	Sun Mar 17 21:53:48 2013 -0400
+++ b/Lib/imaplib.py	Sun Mar 17 20:23:02 2013 -0700
@@ -24,6 +24,7 @@
 
 import binascii, errno, random, re, socket, subprocess, sys, time, calendar
 from datetime import datetime, timezone, timedelta
+from io import BufferedReader, BufferedWriter
 try:
     import ssl
     HAVE_SSL = True
@@ -1246,8 +1247,8 @@
         self.process = subprocess.Popen(self.command,
             stdin=subprocess.PIPE, stdout=subprocess.PIPE,
             shell=True, close_fds=True)
-        self.writefile = self.process.stdin
-        self.readfile = self.process.stdout
+        self.writefile = BufferedWriter(self.process.stdin)
+        self.readfile = BufferedReader(self.process.stdout)
 
     def read(self, size):
         """Read 'size' bytes from remote."""