diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py
index 86e3923..adefa07 100644
--- a/Lib/test/test_math.py
+++ b/Lib/test/test_math.py
@@ -1885,8 +1885,13 @@
             self.assertEqual(perm(n, 1), n)
             self.assertEqual(perm(n, n), factorial(n))
 
+        # Test one argument form
+        for n in range(20):
+            self.assertEqual(perm(n), factorial(n))
+            self.assertEqual(perm(n, None), factorial(n))
+
         # Raises TypeError if any argument is non-integer or argument count is
-        # not 2
+        # not 1 or 2
         self.assertRaises(TypeError, perm, 10, 1.0)
         self.assertRaises(TypeError, perm, 10, decimal.Decimal(1.0))
         self.assertRaises(TypeError, perm, 10, "1")
@@ -1894,7 +1899,7 @@
         self.assertRaises(TypeError, perm, decimal.Decimal(10.0), 1)
         self.assertRaises(TypeError, perm, "10", 1)
 
-        self.assertRaises(TypeError, perm, 10)
+        self.assertRaises(TypeError, perm)
         self.assertRaises(TypeError, perm, 10, 1, 3)
         self.assertRaises(TypeError, perm)