diff --git a/Lib/test/support.py b/Lib/test/support.py
index 83d7ba8..558fbc2 100644
--- a/Lib/test/support.py
+++ b/Lib/test/support.py
@@ -109,7 +109,7 @@
         orig_modules[name] = sys.modules[name]
     except KeyError:
         saved = False
-    sys.modules[name] = 0
+    sys.modules[name] = None
     return saved