Index: Lib/email/test/test_email.py
===================================================================
--- Lib/email/test/test_email.py	(revision 84311)
+++ Lib/email/test/test_email.py	(working copy)
@@ -3089,7 +3089,14 @@
         s = 'Subject: =?EUC-KR?B?CSixpLDtKSC/7Liuvsax4iC6uLmwMcijIKHaILzSwd/H0SC8+LCjwLsgv7W/+Mj3I ?='
         raises(Errors.HeaderParseError, decode_header, s)
 
+    def test_encode_unaliased_charset(self):
+        # Issue 1379416: when the charset was unknown, the output
+        # was accidentally getting coerced to unicode.
+        res = Header('abc','iso-8859-2').encode()
+        self.assertEqual(res, '=?iso-8859-2?q?abc?=')
+        self.assertIsInstance(res, str)
 
+
 
 # Test RFC 2231 header parameters (en/de)coding
 class TestRFC2231(TestEmailBase):