diff -r 9b450b19aa11 Lib/idlelib/IOBinding.py
--- a/Lib/idlelib/IOBinding.py	Sat Jul 12 03:20:40 2014 +0200
+++ b/Lib/idlelib/IOBinding.py	Sat Jul 12 14:19:37 2014 +0300
@@ -65,6 +65,8 @@
 
 coding_re = re.compile(r'^[ \t\f]*#.*coding[:=][ \t]*([-\w.]+)', re.ASCII)
 blank_re = re.compile(r'^[ \t\f]*(?:[#\r\n]|$)', re.ASCII)
+# characters above the range (U+0000-U+FFFF)
+non_bmp_re = re.compile(r'[^\x00-\uffff]')
 
 def coding_spec(data):
     """Return the encoding declaration according to PEP 263.
@@ -231,6 +233,7 @@
         if firsteol:
             self.eol_convention = firsteol.group(0)
             chars = self.eol_re.sub(r"\n", chars)
+        chars = self._fix_non_bmp(chars)
         self.text.delete("1.0", "end")
         self.set_filename(None)
         self.text.insert("1.0", chars)
@@ -313,6 +316,12 @@
             pass
         return None, False  # None on failure
 
+    def _fix_non_bmp(self, s):
+        if s and max(s) > '\uffff':
+            # Tk doesn't support non-BMP characters
+            s = non_bmp_re.sub(lambda m: '\\U%08x' % ord(m.group()), s)
+        return s
+
     def maybesave(self):
         if self.get_saved():
             return "yes"