#11401: handle headers with no value.
diff --git a/Lib/email/header.py b/Lib/email/header.py
index 43220df..da739d5 100644
--- a/Lib/email/header.py
+++ b/Lib/email/header.py
@@ -304,7 +304,7 @@
                                     self._continuation_ws, splitchars)
         for string, charset in self._chunks:
             lines = string.splitlines()
-            formatter.feed(lines[0], charset)
+            formatter.feed(lines[0] if lines else '', charset)
             for line in lines[1:]:
                 formatter.newline()
                 if charset.header_encoding is not None: