diff --git a/ceilometermiddleware/tests/test_swift.py b/ceilometermiddleware/tests/test_swift.py
index 3131b8d..43e0835 100644
--- a/ceilometermiddleware/tests/test_swift.py
+++ b/ceilometermiddleware/tests/test_swift.py
@@ -255,7 +255,7 @@ class TestSwift(tests_base.TestCase):
             self.assertEqual('value1', metadata['http_header_x_var1'])
             self.assertEqual('value2', metadata['http_header_x_var2'])
             self.assertEqual('token', metadata['http_header_token'])
-            self.assertFalse('http_header_x_var3' in metadata)
+            self.assertNotIn('http_header_x_var3', metadata)
 
     def test_metadata_headers_unicode(self):
         app = swift.Swift(FakeApp(), {
diff --git a/tox.ini b/tox.ini
index dabf696..84128a6 100644
--- a/tox.ini
+++ b/tox.ini
@@ -16,7 +16,7 @@ deps =
 commands = stestr run --slowest {posargs}
 
 [testenv:pep8]
-deps = hacking>=3.0.1,<3.1.0
+deps = hacking>=6.1.0,<6.2.0
 commands = flake8
 
 [testenv:venv]