Index: Lib/io.py
===================================================================
--- Lib/io.py	(revision 57506)
+++ Lib/io.py	(working copy)
@@ -1367,6 +1367,7 @@
                 initial_value = str(initial_value)
             self.write(initial_value)
             self.seek(0)
+        self._writetranslate = False
 
     def getvalue(self):
         self.flush()