diff --git a/nova/api/openstack/wsgi.py b/nova/api/openstack/wsgi.py
index 79382d864422..91eeef4b112b 100644
--- a/nova/api/openstack/wsgi.py
+++ b/nova/api/openstack/wsgi.py
@@ -588,7 +588,7 @@ class ResponseObject(object):
         response = webob.Response()
         response.status_int = self.code
         for hdr, value in self._headers.items():
-            response.headers[hdr] = value
+            response.headers[hdr] = str(value)
         response.headers['Content-Type'] = content_type
         if self.obj is not None:
             response.body = serializer.serialize(self.obj)
@@ -1150,6 +1150,8 @@ class Fault(webob.exc.HTTPException):
     def __init__(self, exception):
         """Create a Fault for the given webob.exc.exception."""
         self.wrapped_exc = exception
+        for key, value in self.wrapped_exc.headers.items():
+            self.wrapped_exc.headers[key] = str(value)
         self.status_int = exception.status_int
 
     @webob.dec.wsgify(RequestClass=Request)
diff --git a/nova/tests/api/openstack/compute/test_api.py b/nova/tests/api/openstack/compute/test_api.py
index 9061fd3974ba..da1a4eecea25 100644
--- a/nova/tests/api/openstack/compute/test_api.py
+++ b/nova/tests/api/openstack/compute/test_api.py
@@ -157,7 +157,7 @@ class APITest(test.TestCase):
         if hasattr(exception_type, 'headers'):
             for (key, value) in exception_type.headers.iteritems():
                 self.assertTrue(key in resp.headers)
-                self.assertEquals(resp.headers[key], value)
+                self.assertEquals(resp.headers[key], str(value))
 
     def test_quota_error_mapping(self):
         self._do_test_exception_mapping(exception.QuotaError, 'too many used')
diff --git a/nova/tests/api/openstack/test_faults.py b/nova/tests/api/openstack/test_faults.py
index 1bdb9f8c6ee7..cdec44d23569 100644
--- a/nova/tests/api/openstack/test_faults.py
+++ b/nova/tests/api/openstack/test_faults.py
@@ -68,6 +68,8 @@ class TestFaults(test.TestCase):
 
         for request in requests:
             exc = webob.exc.HTTPRequestEntityTooLarge
+            # NOTE(aloga): we intentionally pass an integer for the
+            # 'Retry-After' header. It should be then converted to a str
             fault = wsgi.Fault(exc(explanation='sorry',
                         headers={'Retry-After': 4}))
             response = request.get_response(fault)
@@ -76,7 +78,7 @@ class TestFaults(test.TestCase):
                 "overLimit": {
                     "message": "sorry",
                     "code": 413,
-                    "retryAfter": 4,
+                    "retryAfter": "4",
                 },
             }
             actual = jsonutils.loads(response.body)
diff --git a/nova/tests/api/openstack/test_wsgi.py b/nova/tests/api/openstack/test_wsgi.py
index 374aa11623f4..a19204dff9c1 100644
--- a/nova/tests/api/openstack/test_wsgi.py
+++ b/nova/tests/api/openstack/test_wsgi.py
@@ -867,6 +867,7 @@ class ResponseObjectTest(test.TestCase):
                                    atom=AtomSerializer)
         robj['X-header1'] = 'header1'
         robj['X-header2'] = 'header2'
+        robj['X-header3'] = 3
 
         for content_type, mtype in wsgi._MEDIA_TYPE_MAP.items():
             request = wsgi.Request.blank('/tests/123')
@@ -875,6 +876,7 @@ class ResponseObjectTest(test.TestCase):
             self.assertEqual(response.headers['Content-Type'], content_type)
             self.assertEqual(response.headers['X-header1'], 'header1')
             self.assertEqual(response.headers['X-header2'], 'header2')
+            self.assertEqual(response.headers['X-header3'], '3')
             self.assertEqual(response.status_int, 202)
             self.assertEqual(response.body, mtype)