diff --git a/flask/helpers.py b/flask/helpers.py
index b2ea2ce9..e4fb8c43 100644
--- a/flask/helpers.py
+++ b/flask/helpers.py
@@ -536,7 +536,7 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
             raise TypeError('filename unavailable, required for '
                             'sending as attachment')
         filename_dict = {
-            'filename': unidecode(attachment_filename),
+            'filename': unidecode(text_type(attachment_filename)),
             'filename*': "UTF-8''%s" % url_quote(attachment_filename)}
         headers.add('Content-Disposition', 'attachment',
                     **filename_dict)
diff --git a/tests/test_helpers.py b/tests/test_helpers.py
index 362b6cfa..f7affb2c 100644
--- a/tests/test_helpers.py
+++ b/tests/test_helpers.py
@@ -565,10 +565,11 @@ class TestSendfile(object):
         with app.test_request_context():
             with open(os.path.join(app.root_path, 'static/index.html')) as f:
                 rv = flask.send_file(f, as_attachment=True,
-                                     attachment_filename='Ñandú／pingüino.txt')
-                value, options = \
-                    parse_options_header(rv.headers['Content-Disposition'])
-                assert options == {'filename': 'Nandu/pinguino.txt', 'filename*': "UTF-8''%C3%91and%C3%BA%EF%BC%8Fping%C3%BCino.txt"}
+                                     attachment_filename=u'Ñandú／pingüino.txt')
+                content_disposition = set(rv.headers['Content-Disposition'].split(';'))
+                assert content_disposition == set(['attachment',
+                                                   ' filename="Nandu/pinguino.txt"',
+                                                   " filename*=UTF-8''%C3%91and%C3%BA%EF%BC%8Fping%C3%BCino.txt"])
                 rv.close()
 
     def test_static_file(self):