diff --git a/Lib/test/test_datetime.py b/Lib/test/test_datetime.py
index ff00d8b0b0d..89fa5c8e697 100644
--- a/Lib/test/test_datetime.py
+++ b/Lib/test/test_datetime.py
@@ -856,6 +856,14 @@ class TestDate(HarmlessMixedComparison, unittest.TestCase):
         # A naive object replaces %z and %Z w/ empty strings.
         self.assertEqual(t.strftime("'%z' '%Z'"), "'' ''")
 
+        #make sure that invalid format specifiers are handled correctly
+        self.assertRaises(ValueError, t.strftime, "%e")
+        self.assertRaises(ValueError, t.strftime, "%")
+        self.assertRaises(ValueError, t.strftime, "%#")
+
+        #check that this standard extension works
+        t.strftime("%f")
+
 
     def test_format(self):
         dt = self.theclass(2007, 9, 10)
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 583df2b4bf6..c89a23f8d69 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -533,6 +533,55 @@ class Win32ErrorTests(unittest.TestCase):
     def test_chmod(self):
         self.assertRaises(WindowsError, os.utime, test_support.TESTFN, 0)
 
+class TestInvalidFD(unittest.TestCase):
+    singles = ["fchdir", "fdopen", "close", "dup", "fdatasync", "fstat",
+               "fstatvfs", "fsync", "tcgetpgrp", "ttyname"]
+    def get_single(f):
+        def helper(self):
+            if  getattr(os, f, None):
+                self.assertRaises(OSError, getattr(os, f), 10)
+        return helper
+    for f in singles:
+        locals()["test_"+f] = get_single(f)
+
+    def test_isatty(self):
+        self.assertEqual(os.isatty(10), False)
+
+    def test_closerange(self):
+        self.assertEqual(os.closerange(10, 20), None)
+
+    def test_dup2(self):
+        self.assertRaises(OSError, os.dup2, 10, 20)
+
+    def test_fchmod(self):
+        if hasattr(os, "fchmod"):
+            self.assertRaises(OSError, os.fchmod, 10, 0)
+
+    def test_fchown(self):
+        if hasattr(os, "fchown"):
+            self.assertRaises(OSError, os.fchmod, 10, -1, -1)
+
+    def test_fpathconf(self):
+        if hasattr(os, "fpathconf"):
+            self.assertRaises(OSError, os.fpathconf, 10, "foo")
+
+    def test_ftruncate(self):
+        if hasattr(os, "ftruncate"):
+            self.assertRaises(OSError, os.ftruncate, 10, 0)
+
+    def test_lseek(self):
+        self.assertRaises(OSError, os.lseek, 10, 0, 0)
+
+    def test_read(self):
+        self.assertRaises(OSError, os.read, 10, 1)
+
+    def test_tcsetpgrpt(self):
+        if hasattr(os, "tcsetpgrp"):
+            self.assertRaises(OSError, os.tcsetpgrp, 10, 0)
+
+    def test_write(self):
+        self.assertRaises(OSError, os.write, 10, " ")
+
 if sys.platform != 'win32':
     class Win32ErrorTests(unittest.TestCase):
         pass
@@ -547,7 +596,8 @@ def test_main():
         MakedirTests,
         DevNullTests,
         URandomTests,
-        Win32ErrorTests
+        Win32ErrorTests,
+        TestInvalidFD
     )
 
 if __name__ == "__main__":