Index: Lib/email/header.py
===================================================================
--- Lib/email/header.py	(revision 87567)
+++ Lib/email/header.py	(working copy)
@@ -245,32 +245,26 @@
         that byte string, and a UnicodeError will be raised if the string
         cannot be decoded with that charset.  If s is a Unicode string, then
         charset is a hint specifying the character set of the characters in
-        the string.  In this case, when producing an RFC 2822 compliant header
-        using RFC 2047 rules, the Unicode string will be encoded using the
-        following charsets in order: us-ascii, the charset hint, utf-8.  The
-        first character set not to provoke a UnicodeError is used.
+        the string.  In either case, when producing an RFC 2822 compliant
+        header using RFC 2047 rules, the string will be encoded using the
+        output charset of the charset hint.  If the string cannot be encoded
+        to the output charset, a UnicodeEncodeError is thrown.
 
-        Optional `errors' is passed as the third argument to any unicode() or
-        ustr.encode() call.
+        Optional `errors' is passed as the errors argument to the decode
+        call if s is a byte string.
         """
         if charset is None:
             charset = self._charset
         elif not isinstance(charset, Charset):
             charset = Charset(charset)
-        if isinstance(s, str):
-            # Convert the string from the input character set to the output
-            # character set and store the resulting bytes and the charset for
-            # composition later.
+        if not isinstance(s, str):
             input_charset = charset.input_codec or 'us-ascii'
-            input_bytes = s.encode(input_charset, errors)
-        else:
-            # We already have the bytes we will store internally.
-            input_bytes = s
+            s = s.decode(input_charset, errors)
         # Ensure that the bytes we're storing can be decoded to the output
         # character set, otherwise an early error is thrown.
         output_charset = charset.output_codec or 'us-ascii'
-        output_string = input_bytes.decode(output_charset, errors)
-        self._chunks.append((output_string, charset))
+        s.encode(output_charset, errors)
+        self._chunks.append((s, charset))
 
     def encode(self, splitchars=';, \t', maxlinelen=None, linesep='\n'):
         """Encode a message header into an RFC-compliant format.
Index: Lib/email/test/test_email.py
===================================================================
--- Lib/email/test/test_email.py	(revision 87549)
+++ Lib/email/test/test_email.py	(working copy)
@@ -3620,8 +3620,12 @@
         s = 'Subject: =?EUC-KR?B?CSixpLDtKSC/7Liuvsax4iC6uLmwMcijIKHaILzSwd/H0SC8+LCjwLsgv7W/+Mj3I ?='
         raises(errors.HeaderParseError, decode_header, s)
 
+    def test_shift_jis_charset(self):
+        h = Header('文', charset='shift_jis')
+        self.assertEqual(h.encode(), '=?iso-2022-jp?b?GyRCSjgbKEI=?=')
 
 
+
 # Test RFC 2231 header parameters (en/de)coding
 class TestRFC2231(TestEmailBase):
     def test_get_param(self):