Index: Lib/test/test_fileio.py
===================================================================
--- Lib/test/test_fileio.py	(revision 68737)
+++ Lib/test/test_fileio.py	(working copy)
@@ -176,6 +176,10 @@
         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"
Index: Modules/_fileio.c
===================================================================
--- Modules/_fileio.c	(revision 68737)
+++ Modules/_fileio.c	(working copy)
@@ -119,7 +119,25 @@
 	return 0;
 }
 
+static int
+check_fd(int fd)
+{
+#if defined(HAVE_FSTAT) && defined(EBADF)
+	struct stat buf;
+	if (fstat(fd, &buf) < 0 && errno == EBADF) {
+		PyObject *exc;
+		char *msg = strerror(EBADF);
+		exc = PyObject_CallFunction(PyExc_OSError, "(is)",
+					    EBADF, msg);
+		PyErr_SetObject(PyExc_OSError, exc);
+		Py_XDECREF(exc);
+		return -1;
+	}
+#endif
+	return 0;
+}
 
+
 static int
 fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 {
@@ -151,6 +169,8 @@
 					"Negative filedescriptor");
 			return -1;
 		}
+		if (check_fd(fd))
+			return -1;
 	}
 	else {
 		PyErr_Clear();