diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 7373334..f7471e5 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -588,7 +588,7 @@
         self.assertRaises(WindowsError, os.utime, support.TESTFN, 0)
 
 class TestInvalidFD(unittest.TestCase):
-    singles = ["fchdir", "dup", "fdatasync", "fstat",
+    singles = ["fchdir", "dup", "fdopen", "fdatasync", "fstat",
                "fstatvfs", "fsync", "tcgetpgrp", "ttyname"]
     #singles.append("close")
     #We omit close because it doesn'r raise an exception on some platforms
diff --git a/Misc/NEWS b/Misc/NEWS
index 592e1a5..1eb8559 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,8 @@
 Core and Builtins
 -----------------
 
+- Issue #4991: os.fdopen now raises an OSError for invalid file descriptors.
+
 - Issue #4838: When a module is deallocated, free the memory backing the
   optional module state data.