diff -r cf90764f40a4 -r 504ef9c49f4a mercurial/util.py
--- a/mercurial/util.py	Mon May 18 23:19:11 2015 -0500
+++ b/mercurial/util.py	Wed May 20 11:29:45 2015 -0500
@@ -247,8 +247,8 @@
     stdin, stdout, stderr, p = popen4(cmd, env, newlines)
     return stdin, stdout, stderr
 
-def popen4(cmd, env=None, newlines=False):
-    p = subprocess.Popen(cmd, shell=True, bufsize=-1,
+def popen4(cmd, env=None, newlines=False, bufsize=-1):
+    p = subprocess.Popen(cmd, shell=True, bufsize=bufsize,
                          close_fds=closefds,
                          stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                          stderr=subprocess.PIPE,