diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index d34c57828b..df6e8a8063 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -791,6 +791,9 @@ class Popen(object):
                 errread = msvcrt.open_osfhandle(errread.Detach(), 0)
 
         self.text_mode = encoding or errors or text or universal_newlines
+        if self.text_mode and not self.encoding:
+            import locale
+            self.encoding = locale.getpreferredencoding(False)
 
         # How long to resume waiting on a child after the first ^C.
         # There is no right value for this.  The purpose is to be polite