fail when negative values are passed to instr()
diff --git a/Lib/test/test_curses.py b/Lib/test/test_curses.py
index ce5f2a5..bdb71e5 100644
--- a/Lib/test/test_curses.py
+++ b/Lib/test/test_curses.py
@@ -187,6 +187,8 @@
 
         self.assertRaises(ValueError, stdscr.getstr, -400)
         self.assertRaises(ValueError, stdscr.getstr, 2, 3, -400)
+        self.assertRaises(ValueError, stdscr.instr, -2)
+        self.assertRaises(ValueError, stdscr.instr, 2, 3, -2)
 
 
     def test_module_funcs(self):