diff -r a1421d28393b Lib/idlelib/PyShell.py
--- a/Lib/idlelib/PyShell.py	Sun Apr 21 17:14:40 2013 -0400
+++ b/Lib/idlelib/PyShell.py	Mon Apr 22 12:47:53 2013 +0300
@@ -642,7 +642,9 @@
         if isinstance(source, types.UnicodeType):
             from idlelib import IOBinding
             try:
-                source = source.encode(IOBinding.encoding)
+                source = '# -*- coding: %s -*-\n%s' % (
+                        IOBinding.encoding,
+                        source.encode(IOBinding.encoding))
             except UnicodeError:
                 self.tkconsole.resetoutput()
                 self.write("Unsupported characters in input\n")