diff --git a/neutron/tests/unit/test_api_v2_resource.py b/neutron/tests/unit/test_api_v2_resource.py
index 91ac57117a..4444c75760 100644
--- a/neutron/tests/unit/test_api_v2_resource.py
+++ b/neutron/tests/unit/test_api_v2_resource.py
@@ -100,8 +100,7 @@ class RequestTestCase(base.BaseTestCase):
         self.assertTrue(self.req.context.is_admin)
 
     def test_best_match_language(self):
-        # Here we test that we are actually invoking language negotiation
-        # by webop and also that the default locale always available is en-US
+        # Test that we are actually invoking language negotiation by webop
         request = wsgi.Request.blank('/')
         gettextutils.get_available_languages = mock.MagicMock()
         gettextutils.get_available_languages.return_value = ['known-language',
@@ -109,9 +108,18 @@ class RequestTestCase(base.BaseTestCase):
         request.headers['Accept-Language'] = 'known-language'
         language = request.best_match_language()
         self.assertEqual(language, 'known-language')
+
+        # If the Accept-Leader is an unknown language, missing or empty,
+        # the best match locale should be None
         request.headers['Accept-Language'] = 'unknown-language'
         language = request.best_match_language()
-        self.assertEqual(language, 'en_US')
+        self.assertEqual(language, None)
+        request.headers['Accept-Language'] = ''
+        language = request.best_match_language()
+        self.assertEqual(language, None)
+        request.headers.pop('Accept-Language')
+        language = request.best_match_language()
+        self.assertEqual(language, None)
 
 
 class ResourceTestCase(base.BaseTestCase):
diff --git a/neutron/wsgi.py b/neutron/wsgi.py
index 35c9746560..6bac0f447e 100644
--- a/neutron/wsgi.py
+++ b/neutron/wsgi.py
@@ -301,10 +301,15 @@ class Request(webob.Request):
         return None
 
     def best_match_language(self):
-        """Determine language for returned response."""
+        """Determines best available locale from the Accept-Language header.
+
+        :returns: the best language match or None if the 'Accept-Language'
+                  header was not available in the request.
+        """
+        if not self.accept_language:
+            return None
         all_languages = gettextutils.get_available_languages('neutron')
-        return self.accept_language.best_match(all_languages,
-                                               default_match='en_US')
+        return self.accept_language.best_match(all_languages)
 
     @property
     def context(self):