Issue #4631: Fix urlopen() result when an HTTP response uses chunked encoding.
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 6265258..30869ac 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -1363,6 +1363,7 @@
             self.assertRaises(ValueError, f.fileno)
             self.assertRaises(ValueError, f.isatty)
             self.assertRaises(ValueError, f.__iter__)
+            self.assertRaises(ValueError, next, f)
             if hasattr(f, "peek"):
                 self.assertRaises(ValueError, f.peek, 1)
             self.assertRaises(ValueError, f.read)