diff --git a/Lib/test/pickletester.py b/Lib/test/pickletester.py
index 01e7a93..71640db 100644
--- a/Lib/test/pickletester.py
+++ b/Lib/test/pickletester.py
@@ -14,6 +14,9 @@
         self.str = str(x)
 
 class initarg(C):
+
+    __safe_for_unpickling__ = 1
+
     def __init__(self, a, b):
         self.a = a
         self.b = b