diff --git a/checkbox-support/checkbox_support/snap_utils/tests/test_config.py b/checkbox-support/checkbox_support/snap_utils/tests/test_config.py
index 0d43332e70..9f4ff9b9b5 100644
--- a/checkbox-support/checkbox_support/snap_utils/tests/test_config.py
+++ b/checkbox-support/checkbox_support/snap_utils/tests/test_config.py
@@ -85,17 +85,17 @@ def test_smoke(self):
         m = mock_open()
         with patch('builtins.open', m):
             write_checkbox_conf({'foo': 'bar'})
-        m().write.called_once_with('[environ]\n')
-        m().write.called_once_with('FOO = bar\n')
-        m().write.called_once_with('\n')
+        m().write.assert_called_with('[environ]\n')
+        m().write.assert_called_with('FOO = bar\n')
+        m().write.assert_called_with('\n')
         self.assertEqual(m().write.call_count, 3)
 
     def test_writes_empty(self):
         m = mock_open()
         with patch('builtins.open', m):
             write_checkbox_conf({})
-        m().write.called_once_with('[environ]\n')
-        m().write.called_once_with('\n')
+        m().write.assert_called_with('[environ]\n')
+        m().write.assert_called_with('\n')
         self.assertEqual(m().write.call_count, 2)