diff -r 33774ca03c96 Lib/email/header.py
--- a/Lib/email/header.py	Thu Feb 03 23:14:58 2011 +0100
+++ b/Lib/email/header.py	Fri Feb 04 12:41:23 2011 +0100
@@ -314,6 +314,8 @@
                                     self._continuation_ws, splitchars)
         for string, charset in self._chunks:
             lines = string.splitlines()
+            if not len(lines):
+                continue
             formatter.feed(lines[0], charset)
             for line in lines[1:]:
                 formatter.newline()