diff --git a/Lib/test/test_zlib.py b/Lib/test/test_zlib.py
index 2ea10a1..c6bdda1 100644
--- a/Lib/test/test_zlib.py
+++ b/Lib/test/test_zlib.py
@@ -85,7 +85,7 @@
 
     def test_baddecompressobj(self):
         # verify failure on building decompress object with bad params
-        self.assertRaises(ValueError, zlib.decompressobj, 0)
+        self.assertRaises(ValueError, zlib.decompressobj, -1)
 
     def test_decompressobj_badflush(self):
         # verify failure on calling decompressobj.flush with bad params