diff --git a/Lib/distutils/tests/test_install.py b/Lib/distutils/tests/test_install.py
index c3492b8..397e2a7 100644
--- a/Lib/distutils/tests/test_install.py
+++ b/Lib/distutils/tests/test_install.py
@@ -26,6 +26,7 @@
 
 
 class InstallTestCase(support.TempdirManager,
+                      support.EnvironGuard,
                       support.LoggingSilencer,
                       unittest.TestCase):
 
diff --git a/Lib/distutils/tests/test_util.py b/Lib/distutils/tests/test_util.py
index 2d7b101..7898e07 100644
--- a/Lib/distutils/tests/test_util.py
+++ b/Lib/distutils/tests/test_util.py
@@ -4,10 +4,11 @@
 from test.test_support import run_unittest
 
 from distutils.errors import DistutilsByteCompileError
+from distutils.tests import support
 from distutils.util import byte_compile, grok_environment_error
 
 
-class UtilTestCase(unittest.TestCase):
+class UtilTestCase(support.EnvironGuard, unittest.TestCase):
 
     def test_dont_write_bytecode(self):
         # makes sure byte_compile raise a DistutilsError