fix bug in 48797808a302
diff --git a/Lib/test/test_mmap.py b/Lib/test/test_mmap.py
index 961aae1..092c4a1 100644
--- a/Lib/test/test_mmap.py
+++ b/Lib/test/test_mmap.py
@@ -661,7 +661,7 @@
         except SystemError:
             self.skipTest("resizing not supported")
         self.assertEqual(m.read(14), '')
-        self.assertRaises(ValueError, m.read_byte,1)
+        self.assertRaises(ValueError, m.read_byte)
         self.assertRaises(ValueError, m.write_byte, 'b')
         self.assertRaises(ValueError, m.write, 'abc')