diff --git a/Lib/test/test_warnings.py b/Lib/test/test_warnings.py
--- a/Lib/test/test_warnings.py
+++ b/Lib/test/test_warnings.py
@@ -451,27 +451,30 @@ class WarnTests(BaseTest):
                       str(cm.exception))
 
         # check that warning instances also raise a TypeError
         with self.assertRaises(TypeError) as cm:
             self.module.warn('bad warning category', MyWarningClass())
         self.assertIn('category must be a Warning subclass, not ',
                       str(cm.exception))
 
-        with self.assertWarns(MyWarningClass) as cm:
-            self.module.warn('good warning category', MyWarningClass)
-        self.assertEqual('good warning category', str(cm.warning))
+        with original_warnings.catch_warnings(module=self.module):
+            self.module.resetwarnings()
+            self.module.filterwarnings('default')
+            with self.assertWarns(MyWarningClass) as cm:
+                self.module.warn('good warning category', MyWarningClass)
+            self.assertEqual('good warning category', str(cm.warning))
 
-        with self.assertWarns(UserWarning) as cm:
-            self.module.warn('good warning category', None)
-        self.assertEqual('good warning category', str(cm.warning))
+            with self.assertWarns(UserWarning) as cm:
+                self.module.warn('good warning category', None)
+            self.assertEqual('good warning category', str(cm.warning))
 
-        with self.assertWarns(MyWarningClass) as cm:
-            self.module.warn('good warning category', MyWarningClass)
-        self.assertIsInstance(cm.warning, Warning)
+            with self.assertWarns(MyWarningClass) as cm:
+                self.module.warn('good warning category', MyWarningClass)
+            self.assertIsInstance(cm.warning, Warning)
 
 class CWarnTests(WarnTests, unittest.TestCase):
     module = c_warnings
 
     # As an early adopter, we sanity check the
     # test.support.import_fresh_module utility function
     def test_accelerated(self):
         self.assertFalse(original_warnings is self.module)