Index: Lib/email/test/test_email.py
===================================================================
--- Lib/email/test/test_email.py	(révision 67201)
+++ Lib/email/test/test_email.py	(copie de travail)
@@ -3387,6 +3387,25 @@
 
 
 
+# Test some badly formatted messages
+class TestUnicode(TestEmailBase):
+    def test_header(self):
+        msg = MIMEText('accent \xe9\xf4\u0142', 'plain', 'utf-8')
+        msg['Subject'] = 'sujet \xe9\xf4\u0142'
+        msg['From'] = 'toto@localhost'
+        msg['To'] = 'toto@localhost'
+        self.assertEqual(msg.as_string(), """Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: base64
+Subject: =?utf-8?b?c3VqZXQgw6nDtMWC?=
+From: toto@localhost
+To: toto@localhost
+
+YWNjZW50IMOpw7TFgg==
+""")
+
+
+
 def _testclasses():
     mod = sys.modules[__name__]
     return [getattr(mod, name) for name in dir(mod) if name.startswith('Test')]
Index: Lib/email/generator.py
===================================================================
--- Lib/email/generator.py	(révision 67201)
+++ Lib/email/generator.py	(copie de travail)
@@ -105,7 +105,7 @@
         # handle that itself.  If not, we'll do it generically.
         meth = getattr(msg, '_write_headers', None)
         if meth is None:
-            self._write_headers(msg)
+            self._write_headers(msg, msg._charset)
         else:
             meth(self)
         self._fp.write(sfp.getvalue())
@@ -130,14 +130,19 @@
     # Default handlers
     #
 
-    def _write_headers(self, msg):
+    def _write_headers(self, msg, charset):
         for h, v in msg.items():
             print('%s:' % h, end=' ', file=self._fp)
             if isinstance(v, Header):
                 print(v.encode(maxlinelen=self._maxheaderlen), file=self._fp)
             else:
                 # Header's got lots of smarts, so use it.
-                header = Header(v, maxlinelen=self._maxheaderlen,
+                try:
+                    vascii = v.encode('ASCII')
+                    header_charset = None
+                except UnicodeEncodeError:
+                    header_charset = charset
+                header = Header(v, header_charset, maxlinelen=self._maxheaderlen,
                                 header_name=h, continuation_ws='\t')
                 print(header.encode(), file=self._fp)
         # A blank line always separates headers from body