diff -r 6bce7c6d0502 Lib/ConfigParser.py
--- a/Lib/ConfigParser.py	Tue Apr 07 07:09:06 2015 -0400
+++ b/Lib/ConfigParser.py	Wed Apr 08 15:02:56 2015 +1000
@@ -240,6 +240,10 @@
             self._optcre = self.OPTCRE
         if defaults:
             for key, value in defaults.items():
+                if not isinstance(key, basestring):
+                    key = str(key)
+                if not isinstance(value, basestring):
+                    value = str(value)
                 self._defaults[self.optionxform(key)] = value
 
     def defaults(self):