diff --git a/os_win/tests/unit/test_base.py b/os_win/tests/unit/test_base.py
index 6ea48190..101e67c3 100644
--- a/os_win/tests/unit/test_base.py
+++ b/os_win/tests/unit/test_base.py
@@ -19,6 +19,7 @@ from oslotest import base
 from six.moves import builtins
 
 from os_win import exceptions
+from os_win.utils import baseutils
 
 
 class TestingException(Exception):
@@ -37,6 +38,7 @@ class OsWinBaseTestCase(base.BaseTestCase):
         super(OsWinBaseTestCase, self).setUp()
 
         self._mock_wmi = mock.MagicMock()
+        baseutils.BaseUtilsVirt._old_wmi = self._mock_wmi
 
         mock_os = mock.MagicMock(Version='6.3.0')
         self._mock_wmi.WMI.return_value.Win32_OperatingSystem.return_value = (
diff --git a/os_win/tests/unit/utils/test_baseutils.py b/os_win/tests/unit/utils/test_baseutils.py
index 0e158ef3..e967c228 100644
--- a/os_win/tests/unit/utils/test_baseutils.py
+++ b/os_win/tests/unit/utils/test_baseutils.py
@@ -100,6 +100,7 @@ class BaseUtilsVirtTestCase(test_base.OsWinBaseTestCase):
     @mock.patch.object(baseutils, 'imp')
     @mock.patch.object(baseutils, 'wmi', create=True)
     def test_vs_man_svc_2012(self, mock_wmi, mock_imp):
+        baseutils.BaseUtilsVirt._old_wmi = None
         mock_os = mock.MagicMock(Version='6.2.0')
         mock_wmi.WMI.return_value.Win32_OperatingSystem.return_value = [
             mock_os]