diff -r c964820dfbc0 Objects/longobject.c
--- a/Objects/longobject.c	Fri Sep 26 12:43:40 2014 +0200
+++ b/Objects/longobject.c	Fri Sep 26 12:53:31 2014 +0200
@@ -2941,10 +2941,23 @@
 long_add(PyLongObject *a, PyLongObject *b)
 {
     PyLongObject *z;
+    Py_ssize_t a_size, b_size;
 
     CHECK_BINOP(a, b);
 
-    if (Py_ABS(Py_SIZE(a)) <= 1 && Py_ABS(Py_SIZE(b)) <= 1) {
+    a_size = Py_ABS(Py_SIZE(a));
+    b_size = Py_ABS(Py_SIZE(b));
+
+    if (a_size == 0) {
+        Py_INCREF(b);
+        return (PyObject*)b;
+    }
+    if (b_size == 0) {
+        Py_INCREF(a);
+        return (PyObject*)a;
+    }
+
+    if (a_size == 1 && b_size == 1) {
         PyObject *result = PyLong_FromLong(MEDIUM_VALUE(a) +
                                           MEDIUM_VALUE(b));
         return result;
@@ -2971,10 +2984,22 @@
 long_sub(PyLongObject *a, PyLongObject *b)
 {
     PyLongObject *z;
+    Py_ssize_t a_size, b_size;
 
     CHECK_BINOP(a, b);
 
-    if (Py_ABS(Py_SIZE(a)) <= 1 && Py_ABS(Py_SIZE(b)) <= 1) {
+    a_size = Py_ABS(Py_SIZE(a));
+    b_size = Py_ABS(Py_SIZE(b));
+
+    if (b_size == 0) {
+        Py_INCREF(a);
+        return (PyObject*)a;
+    }
+    if (a_size == 0) {
+        return long_neg(b);
+    }
+
+    if (a_size == 1 && b_size == 1) {
         PyObject* r;
         r = PyLong_FromLong(MEDIUM_VALUE(a)-MEDIUM_VALUE(b));
         return r;