diff --git a/Lib/test/test_fileio.py b/Lib/test/test_fileio.py
index 817103e..69aa3fd 100644
--- a/Lib/test/test_fileio.py
+++ b/Lib/test/test_fileio.py
@@ -175,6 +175,10 @@
         f.close()
         os.unlink(TESTFN)
 
+    def testInvalidFd(self):
+        self.assertRaises(ValueError, _fileio._FileIO, -10)
+        self.assertRaises(OSError, _fileio._FileIO, 10)
+
     def testBadModeArgument(self):
         # verify that we get a sensible error message for bad mode argument
         bad_mode = "qwerty"