As per Armin Rigo's suggestion, remove special handing from intobject.c to deal with the peculiarities of classobject's implementation of the number protocol.  The nb_long method of classobject now falls back to nb_int if there is no __long__ attribute present.
diff --git a/Objects/classobject.c b/Objects/classobject.c
index 8560b68..89cca59 100644
--- a/Objects/classobject.c
+++ b/Objects/classobject.c
@@ -1539,6 +1539,18 @@
 	return generic_unary_op(self, o); \
 }
 
+/* unary function with a fallback */
+#define UNARY_FB(funcname, methodname, funcname_fb) \
+static PyObject *funcname(PyInstanceObject *self) { \
+	static PyObject *o; \
+	if (o == NULL) { o = PyString_InternFromString(methodname); \
+			 if (o == NULL) return NULL; } \
+	if (PyObject_HasAttr((PyObject*)self, o)) \
+		return generic_unary_op(self, o); \
+	else \
+		return funcname_fb(self); \
+}
+
 #define BINARY(f, m, n) \
 static PyObject *f(PyObject *v, PyObject *w) { \
 	return do_binop(v, w, "__" m "__", "__r" m "__", n); \
@@ -1777,7 +1789,7 @@
 
 UNARY(instance_invert, "__invert__")
 UNARY(instance_int, "__int__")
-UNARY(instance_long, "__long__")
+UNARY_FB(instance_long, "__long__", instance_int)
 UNARY(instance_float, "__float__")
 UNARY(instance_oct, "__oct__")
 UNARY(instance_hex, "__hex__")
diff --git a/Objects/intobject.c b/Objects/intobject.c
index a82b3c8..9333a55 100644
--- a/Objects/intobject.c
+++ b/Objects/intobject.c
@@ -213,15 +213,10 @@
 		return -1;
 	}
 
-	if (nb->nb_long != 0) {
+	if (nb->nb_long != 0)
 		io = (PyIntObject*) (*nb->nb_long) (op);
-		if (io == NULL && PyErr_ExceptionMatches(PyExc_AttributeError)) {
-			PyErr_Clear();
-			io = (PyIntObject*) (*nb->nb_int) (op);
-		}
-	} else {
+	else
 		io = (PyIntObject*) (*nb->nb_int) (op);
-	}
 	if (io == NULL)
 		return -1;
 	if (!PyInt_Check(io)) {