diff --git a/flask/helpers.py b/flask/helpers.py
index 19d33420..420467ad 100644
--- a/flask/helpers.py
+++ b/flask/helpers.py
@@ -14,10 +14,10 @@ import sys
 import pkgutil
 import posixpath
 import mimetypes
-from unicodedata import normalize
 from time import time
 from zlib import adler32
 from threading import RLock
+import unicodedata
 from werkzeug.routing import BuildError
 from functools import update_wrapper
 
@@ -478,6 +478,11 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
     .. versionchanged:: 0.12
        The `attachment_filename` is preferred over `filename` for MIME-type
        detection.
+       
+    .. versionchanged:: 0.13
+        UTF-8 filenames, as specified in `RFC 2231`_, are supported.
+        
+    .. _RFC 2231: https://tools.ietf.org/html/rfc2231#section-4
 
     :param filename_or_fp: the filename of the file to send in `latin-1`.
                            This is relative to the :attr:`~Flask.root_path`
@@ -535,7 +540,10 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
         if attachment_filename is None:
             raise TypeError('filename unavailable, required for '
                             'sending as attachment')
-        normalized = normalize('NFKD', text_type(attachment_filename))
+
+        normalized = unicodedata.normalize(
+            'NFKD', text_type(attachment_filename)
+        )
 
         try:
             normalized.encode('ascii')
@@ -545,12 +553,9 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
                 'filename*': "UTF-8''%s" % url_quote(attachment_filename),
             }
         else:
-            filenames = {
-                'filename': attachment_filename,
-            }
+            filenames = {'filename': attachment_filename}
 
-        headers.add('Content-Disposition', 'attachment',
-                    **filenames)
+        headers.add('Content-Disposition', 'attachment', **filenames)
 
     if current_app.use_x_sendfile and filename:
         if file is not None:
diff --git a/tests/test_helpers.py b/tests/test_helpers.py
index f7affb2c..1aeff065 100644
--- a/tests/test_helpers.py
+++ b/tests/test_helpers.py
@@ -540,10 +540,11 @@ class TestSendfile(object):
                 value, options = \
                     parse_options_header(rv.headers['Content-Disposition'])
                 assert value == 'attachment'
+                assert options['filename'] == 'index.html'
+                assert 'filename*' not in options
                 rv.close()
 
         with app.test_request_context():
-            assert options['filename'] == 'index.html'
             rv = flask.send_file('static/index.html', as_attachment=True)
             value, options = parse_options_header(rv.headers['Content-Disposition'])
             assert value == 'attachment'
@@ -562,15 +563,21 @@ class TestSendfile(object):
 
     def test_attachment_with_utf8_filename(self):
         app = flask.Flask(__name__)
+
         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=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()
+            rv = flask.send_file(
+                'static/index.html', as_attachment=True,
+                attachment_filename=u'Ñandú／pingüino.txt'
+            )
+            value, options = parse_options_header(
+                rv.headers['Content-Disposition']
+            )
+            rv.close()
+
+        assert value == 'attachment'
+        assert sorted(options.keys()) == ('filename', 'filename*')
+        assert options['filename'] == 'Nandu/pinguino.txt'
+        assert options['filename*'] == 'UTF-8''%C3%91and%C3%BA%EF%BC%8Fping%C3%BCino.txt'
 
     def test_static_file(self):
         app = flask.Flask(__name__)