diff --git a/flanker/mime/message/headers/encoding.py b/flanker/mime/message/headers/encoding.py
index 672d69c..3ee6449 100644
--- a/flanker/mime/message/headers/encoding.py
+++ b/flanker/mime/message/headers/encoding.py
@@ -10,7 +10,7 @@
 
 _log = logging.getLogger(__name__)
 
-_ADDRESS_HEADERS = ('From', 'To', 'Delivered-To', 'Cc', 'Bcc', 'Reply-To')
+_ADDRESS_HEADERS = ('From', 'To', 'Delivered-To', 'Cc', 'Bcc', 'Reply-To', 'Sender')
 
 
 def to_mime(key, value):