diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index f6f6b26..7b6d82b 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -101,6 +101,8 @@
         _thread.start_new_thread(f, ())
         done.wait()
         self.assertFalse(ident[0] is None)
+        # Kill the "immortal" _DummyThread
+        del threading._active[ident[0]]
 
     # run with a small(ish) thread stack size (256kB)
     def test_various_ops_small_stack(self):