diff --git a/acme/client_test.py b/acme/client_test.py
index bbed2ed87..a524989e3 100644
--- a/acme/client_test.py
+++ b/acme/client_test.py
@@ -503,7 +503,8 @@ class ClientNetworkWithMockedResponseTest(unittest.TestCase):
 
     def test_head(self):
         self.assertEqual(self.response, self.net.head('url', 'foo', bar='baz'))
-        self.send_request.assert_called_once('HEAD', 'url', 'foo', bar='baz')
+        self.send_request.assert_called_once_with(
+            'HEAD', 'url', 'foo', bar='baz')
 
     def test_get(self):
         self.assertEqual(self.checked_response, self.net.get(
diff --git a/letsencrypt/plugins/manual_test.py b/letsencrypt/plugins/manual_test.py
index a533bcc75..9daba668a 100644
--- a/letsencrypt/plugins/manual_test.py
+++ b/letsencrypt/plugins/manual_test.py
@@ -41,7 +41,7 @@ class ManualAuthenticatorTest(unittest.TestCase):
 
         resp = challenges.SimpleHTTPResponse(tls=False, path='Zm9v')
         self.assertEqual([resp], self.auth.perform(self.achalls))
-        mock_raw_input.assert_called_once()
+        self.assertEqual(1, mock_raw_input.call_count)
         mock_verify.assert_called_with(self.achalls[0].challb, "foo.com", 4430)
 
         message = mock_stdout.write.mock_calls[0][1][0]
diff --git a/letsencrypt/tests/cli_test.py b/letsencrypt/tests/cli_test.py
index 130da4217..613c3189b 100644
--- a/letsencrypt/tests/cli_test.py
+++ b/letsencrypt/tests/cli_test.py
@@ -45,7 +45,7 @@ class CLITest(unittest.TestCase):
 
     def test_rollback(self):
         _, _, _, client = self._call(['rollback'])
-        client.rollback.assert_called_once()
+        self.assertEqual(1, client.rollback.call_count)
 
         _, _, _, client = self._call(['rollback', '--checkpoints', '123'])
         client.rollback.assert_called_once_with(
@@ -53,7 +53,7 @@ class CLITest(unittest.TestCase):
 
     def test_config_changes(self):
         _, _, _, client = self._call(['config_changes'])
-        client.view_config_changes.assert_called_once()
+        self.assertEqual(1, client.view_config_changes.call_count)
 
     def test_plugins(self):
         flags = ['--init', '--prepare', '--authenticators', '--installers']
diff --git a/letsencrypt/tests/display/ops_test.py b/letsencrypt/tests/display/ops_test.py
index 6f4b2f317..273687128 100644
--- a/letsencrypt/tests/display/ops_test.py
+++ b/letsencrypt/tests/display/ops_test.py
@@ -80,11 +80,11 @@ class PickPluginTest(unittest.TestCase):
     def test_default_provided(self):
         self.default = "foo"
         self._call()
-        self.reg.filter.assert_called_once()
+        self.assertEqual(1, self.reg.filter.call_count)
 
     def test_no_default(self):
         self._call()
-        self.reg.filter.assert_called_once()
+        self.assertEqual(1, self.reg.filter.call_count)
 
     def test_no_candidate(self):
         self.assertTrue(self._call() is None)