diff -r f494052eb476 Lib/test/test_long.py
--- a/Lib/test/test_long.py	Mon Feb 08 20:28:22 2016 +0200
+++ b/Lib/test/test_long.py	Mon Feb 08 17:28:52 2016 -0500
@@ -689,6 +689,14 @@
         self.assertRaises(OverflowError, int, float('-inf'))
         self.assertRaises(ValueError, int, float('nan'))
 
+    def test_mod_division(self):
+        with self.assertRaises(ZeroDivisionError):
+            _ = 1 % 0
+        self.assertEqual(13 % 10, 3)
+        self.assertEqual(-13 % 10, 7)
+        self.assertEqual(13 % -10, -7)
+        self.assertEqual(-13 % -10, -3)
+
     def test_true_division(self):
         huge = 1 << 40000
         mhuge = -huge
diff -r f494052eb476 Objects/longobject.c
--- a/Objects/longobject.c	Mon Feb 08 20:28:22 2016 +0200
+++ b/Objects/longobject.c	Mon Feb 08 17:28:52 2016 -0500
@@ -3848,6 +3848,26 @@
 
     CHECK_BINOP(a, b);
 
+    if (Py_ABS(Py_SIZE(a)) == 1 && Py_ABS(Py_SIZE(b)) == 1) {
+        /* Fast path for single-digit longs. See the comment for
+           l_divmod function, which explains the algorithm. */
+        sdigit left = ((PyLongObject*)a)->ob_digit[0];
+        sdigit right = ((PyLongObject*)b)->ob_digit[0];
+        sdigit mod = left % right;
+
+        if (Py_SIZE(a) < 0 || Py_SIZE(b) < 0) {
+            mod *= Py_SIZE(a);
+            if (mod < 0 && Py_SIZE(b) > 0) {
+                mod += right;
+            }
+            else if (mod > 0 && Py_SIZE(b) < 0) {
+                mod -= right;
+            }
+        }
+
+        return PyLong_FromLong(mod);
+    }
+
     if (l_divmod((PyLongObject*)a, (PyLongObject*)b, NULL, &mod) < 0)
         mod = NULL;
     return (PyObject *)mod;