diff --git a/barbicanclient/tests/test_client.py b/barbicanclient/tests/test_client.py
index 22b104b9..d2e18792 100644
--- a/barbicanclient/tests/test_client.py
+++ b/barbicanclient/tests/test_client.py
@@ -105,7 +105,7 @@ class WhenTestingClientPost(TestClient):
     def test_post_checks_status_code(self):
         self.httpclient._check_status_code = mock.MagicMock()
         self.httpclient.post(path='secrets', json={'test_data': 'test'})
-        self.httpclient._check_status_code.assert_called()
+        self.assertTrue(self.httpclient._check_status_code.called)
 
 
 class WhenTestingClientGet(TestClient):
@@ -144,7 +144,7 @@ class WhenTestingClientGet(TestClient):
     def test_get_checks_status_code(self):
         self.httpclient._check_status_code = mock.MagicMock()
         self.httpclient.get(self.href)
-        self.httpclient._check_status_code.assert_called()
+        self.assertTrue(self.httpclient._check_status_code.called)
 
     def test_get_raw_uses_href_as_is(self):
         self.httpclient._get_raw(self.href, headers=self.headers)
@@ -163,7 +163,7 @@ class WhenTestingClientGet(TestClient):
     def test_get_raw_checks_status_code(self):
         self.httpclient._check_status_code = mock.MagicMock()
         self.httpclient._get_raw(self.href, headers=self.headers)
-        self.httpclient._check_status_code.assert_called()
+        self.assertTrue(self.httpclient._check_status_code.called)
 
 
 class WhenTestingClientDelete(TestClient):
@@ -194,7 +194,7 @@ class WhenTestingClientDelete(TestClient):
     def test_delete_checks_status_code(self):
         self.httpclient._check_status_code = mock.MagicMock()
         self.httpclient.delete(self.href)
-        self.httpclient._check_status_code.assert_called()
+        self.assertTrue(self.httpclient._check_status_code.called)
 
 
 class WhenTestingCheckStatusCodes(TestClient):
diff --git a/test-requirements.txt b/test-requirements.txt
index 8f21346e..07020c9e 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -6,7 +6,8 @@ discover
 hacking<0.11,>=0.10.0
 fixtures>=1.3.1
 requests-mock>=0.6.0 # Apache-2.0
-mock>=1.0
+mock>=1.0;python_version!='2.6'
+mock==1.0.1;python_version=='2.6'
 testrepository>=0.0.18
 testtools>=1.4.0
 oslotest>=1.5.1 # Apache-2.0