diff --git a/Lib/email/header.py b/Lib/email/header.py
--- a/Lib/email/header.py
+++ b/Lib/email/header.py
@@ -70,7 +70,7 @@
     occurs (e.g. a base64 decoding exception).
     """
     # If no encoding, just return the header with no charset.
-    if not ecre.search(header):
+    if not ecre.search(str(header)):
         return [(header, None)]
     # First step is to parse all the encoded parts into triplets of the form
     # (encoded_string, encoding, charset).  For unencoded strings, the last
@@ -265,6 +265,9 @@
             charset = self._charset
         elif not isinstance(charset, Charset):
             charset = Charset(charset)
+        # Steffen is out now
+        if isinstance(s, email.header.Header):
+            s = str(s)
         if not isinstance(s, str):
             input_charset = charset.input_codec or 'us-ascii'
             s = s.decode(input_charset, errors)