diff --git a/sendfile/__init__.py b/sendfile/__init__.py
index 1cc9809..1c1d4c7 100644
--- a/sendfile/__init__.py
+++ b/sendfile/__init__.py
@@ -2,6 +2,7 @@
 __version__ = '.'.join(map(str, VERSION))
 
 import os.path
+import sys
 from mimetypes import guess_type
 import unicodedata
 
@@ -78,6 +79,9 @@ def sendfile(request, filename, attachment=False, attachment_filename=None, mime
                 from django.utils.encoding import force_unicode as force_text
             attachment_filename = force_text(attachment_filename)
             ascii_filename = unicodedata.normalize('NFKD', attachment_filename).encode('ascii','ignore') 
+            if sys.version_info[0] >= 3:
+                # We want ascii_filename as a unicode string, since it will be formatted into parts
+                ascii_filename = ascii_filename.decode('ascii')
             parts.append('filename="%s"' % ascii_filename)
             if ascii_filename != attachment_filename:
                 from django.utils.http import urlquote