diff --git a/hgext/convert/cvs.py b/hgext/convert/cvs.py
--- a/hgext/convert/cvs.py
+++ b/hgext/convert/cvs.py
@@ -267,7 +267,7 @@ class convert_cvs(converter_source):
             # popen2 does not support argument lists under Windows
             cmd = [util.shellquote(arg) for arg in cmd]
             cmd = util.quotecommand(' '.join(cmd))
-            self.writep, self.readp = util.popen2(cmd, 'b')
+            self.writep, self.readp = util.popen2(cmd)
 
         self.realroot = root
 
diff --git a/hgext/convert/subversion.py b/hgext/convert/subversion.py
--- a/hgext/convert/subversion.py
+++ b/hgext/convert/subversion.py
@@ -987,7 +987,7 @@ class svn_source(converter_source):
         arg = encodeargs(args)
         hgexe = util.hgexecutable()
         cmd = '%s debugsvnlog' % util.shellquote(hgexe)
-        stdin, stdout = util.popen2(cmd, 'b')
+        stdin, stdout = util.popen2(cmd)
         stdin.write(arg)
         stdin.close()
         return logstream(stdout)
diff --git a/mercurial/sshrepo.py b/mercurial/sshrepo.py
--- a/mercurial/sshrepo.py
+++ b/mercurial/sshrepo.py
@@ -62,7 +62,7 @@ class sshrepository(repo.repository):
 
         cmd = util.quotecommand(cmd)
         ui.note(_('running %s\n') % cmd)
-        self.pipeo, self.pipei, self.pipee = util.popen3(cmd, 'b')
+        self.pipeo, self.pipei, self.pipee = util.popen3(cmd)
 
         # skip any noise generated by remote shell
         self.do_cmd("hello")
diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -38,12 +38,12 @@ def _fastsha1(s):
 
 import subprocess
 closefds = os.name == 'posix'
-def popen2(cmd, mode='t', bufsize=-1):
+def popen2(cmd, bufsize=-1):
     p = subprocess.Popen(cmd, shell=True, bufsize=bufsize,
                          close_fds=closefds,
                          stdin=subprocess.PIPE, stdout=subprocess.PIPE)
     return p.stdin, p.stdout
-def popen3(cmd, mode='t', bufsize=-1):
+def popen3(cmd, bufsize=-1):
     p = subprocess.Popen(cmd, shell=True, bufsize=bufsize,
                          close_fds=closefds,
                          stdin=subprocess.PIPE, stdout=subprocess.PIPE,