diff --git a/nova/api/openstack/placement/handler.py b/nova/api/openstack/placement/handler.py
index 5d5377f4c835..d10fadd8855b 100644
--- a/nova/api/openstack/placement/handler.py
+++ b/nova/api/openstack/placement/handler.py
@@ -107,7 +107,11 @@ def handle_405(environ, start_response):
     _methods = util.wsgi_path_item(environ, '_methods')
     headers = {}
     if _methods:
-        headers['allow'] = _methods
+        # Ensure allow header is a python 2 or 3 native string (thus
+        # not unicode in python 2 but stay a string in python 3)
+        # In the process done by Routes to save the allowed methods
+        # to its routing table they become unicode in py2.
+        headers['allow'] = str(_methods)
     raise webob.exc.HTTPMethodNotAllowed(
         _('The method specified is not allowed for this resource.'),
         headers=headers, json_formatter=util.json_error_formatter)
diff --git a/nova/tests/functional/api/openstack/placement/test_placement_api.py b/nova/tests/functional/api/openstack/placement/test_placement_api.py
index 9fadc70fd96a..42cbc75ab829 100644
--- a/nova/tests/functional/api/openstack/placement/test_placement_api.py
+++ b/nova/tests/functional/api/openstack/placement/test_placement_api.py
@@ -12,11 +12,16 @@
 
 import os
 
+import wsgi_intercept
+
 from gabbi import driver
 
 from nova.tests import fixtures as nova_fixtures
 from nova.tests.functional.api.openstack.placement import fixtures
 
+# Check that wsgi application response headers are always
+# native str.
+wsgi_intercept.STRICT_RESPONSE_HEADERS = True
 TESTS_DIR = 'gabbits'
 
 
diff --git a/nova/tests/unit/api/openstack/placement/test_handler.py b/nova/tests/unit/api/openstack/placement/test_handler.py
index b0a81e15efcd..6a07343978f3 100644
--- a/nova/tests/unit/api/openstack/placement/test_handler.py
+++ b/nova/tests/unit/api/openstack/placement/test_handler.py
@@ -92,12 +92,24 @@ class MapperTest(test.NoDBTestCase):
         action = self.mapper.match(environ=environ)['action']
         self.assertEqual('hello', action)
 
-    def test_405(self):
+    def test_405_methods(self):
         environ = _environ(path='/hello', method='POST')
         result = self.mapper.match(environ=environ)
         self.assertEqual(handler.handle_405, result['action'])
         self.assertEqual('GET', result['_methods'])
 
+    def test_405_headers(self):
+        environ = _environ(path='/hello', method='POST')
+        error = self.assertRaises(webob.exc.HTTPMethodNotAllowed,
+                                  handler.dispatch,
+                                  environ, start_response,
+                                  self.mapper)
+        allow_header = error.headers['allow']
+        self.assertEqual('GET', allow_header)
+        # PEP 3333 requires that headers be whatever the native str
+        # is in that version of Python. Never unicode.
+        self.assertEqual(str, type(allow_header))
+
 
 class PlacementLoggingTest(test.NoDBTestCase):