diff --git a/Lib/test/test_py3kwarn.py b/Lib/test/test_py3kwarn.py
new file mode 100644
index 0000000..61de7a2
--- /dev/null
+++ b/Lib/test/test_py3kwarn.py
@@ -0,0 +1,60 @@
+import unittest
+from test.test_support import catch_warning, TestSkipped, run_unittest
+import warnings
+
+# TODO: This is a hack to raise TestSkipped if -3 is not enabled. Instead
+# of relying on callable to have a warning, we should expose the -3 flag
+# to Python code somehow
+with catch_warning() as w:
+    callable(int)
+    if w.message is None:
+        raise TestSkipped('%s must be run with the -3 flag' % __name__)
+
+class TestPy3KWarnings(unittest.TestCase):
+
+    def test_type_inequality_comparisons(self):
+        expected = 'type inequality comparisons not supported in 3.x.'
+        with catch_warning() as w:
+            self.assertWarning(int < str, w, expected)
+        with catch_warning() as w:
+            self.assertWarning(type < object, w, expected)
+
+    def test_object_inequality_comparisons(self):
+        expected = 'comparing unequal types not supported in 3.x.'
+        with catch_warning() as w:
+            self.assertWarning(str < [], w, expected)
+        with catch_warning() as w:
+            self.assertWarning(object() < (1, 2), w, expected)
+
+    def test_dict_inequality_comparisons(self):
+        expected = 'dict inequality comparisons not supported in 3.x.'
+        with catch_warning() as w:
+            self.assertWarning({} < {2:3}, w, expected)
+        with catch_warning() as w:
+            self.assertWarning({} <= {}, w, expected)
+        with catch_warning() as w:
+            self.assertWarning({} > {2:3}, w, expected)
+        with catch_warning() as w:
+            self.assertWarning({2:3} >= {}, w, expected)
+
+    def test_cell_inequality_comparisons(self):
+        expected = 'cell comparisons not supported in 3.x.'
+        def f(x):
+            def g():
+                return x
+            return g
+        cell0, = f(0).func_closure
+        cell1, = f(1).func_closure
+        with catch_warning() as w:
+            self.assertWarning(cell0 == cell1, w, expected)
+        with catch_warning() as w:
+            self.assertWarning(cell0 < cell1, w, expected)
+
+    def assertWarning(self, _, warning, expected_message):
+        self.assertEqual(str(warning.message), expected_message)
+
+def test_main():
+    run_unittest(TestPy3KWarnings)
+
+if __name__ == '__main__':
+    test_main()
diff --git a/Lib/test/test_undocumented_details.py b/Lib/test/test_undocumented_details.py
new file mode 100644
index 0000000..ca66c19
--- /dev/null
+++ b/Lib/test/test_undocumented_details.py
@@ -0,0 +1,39 @@
+from test.test_support import run_unittest, have_unicode
+import unittest
+import sys
+
+class TestImplementationComparisons(unittest.TestCase):
+
+    def test_type_comparisons(self):
+        self.assertTrue(str < int or str > int)
+        self.assertTrue(int <= str or int >= str)
+        self.assertTrue(cmp(int, str) != 0)
+        self.assertTrue(int is int)
+        self.assertTrue(str == str)
+        self.assertTrue(int != str)
+
+    def test_cell_comparisons(self):
+        def f(x):
+            if x:
+                y = 1
+            def g():
+                return x
+            def h():
+                return y
+            return g, h
+        g, h = f(0)
+        g_cell, = g.func_closure
+        h_cell, = h.func_closure
+        self.assertTrue(h_cell < g_cell)
+        self.assertTrue(g_cell >= h_cell)
+        self.assertEqual(cmp(g_cell, h_cell), 1)
+        self.assertTrue(g_cell is g_cell)
+        self.assertTrue(g_cell == g_cell)
+        self.assertTrue(h_cell == h_cell)
+        self.assertTrue(g_cell != h_cell)
+
+def test_main():
+    run_unittest(TestImplementationComparisons)
+
+if __name__ == '__main__':
+    test_main()
diff --git a/Objects/cellobject.c b/Objects/cellobject.c
index b72d43b..37cde41 100644
--- a/Objects/cellobject.c
+++ b/Objects/cellobject.c
@@ -54,6 +54,12 @@
 static int
 cell_compare(PyCellObject *a, PyCellObject *b)
 {
+	/* Py3K warning for comparisons  */
+	if (Py_Py3kWarningFlag && PyErr_Warn(PyExc_DeprecationWarning,
+			"cell comparisons not supported in 3.x.") < 0) {
+		return NULL;
+	}
+
 	if (a->ob_ref == NULL) {
 		if (b->ob_ref == NULL)
 			return 0;
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 1246785..1ca2830 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -1776,8 +1776,14 @@
 			return NULL;
 		res = (cmp == (op == Py_EQ)) ? Py_True : Py_False;
 	}
-	else
+	else {
+		/* Py3K warning if comparison isn't == or !=  */
+		if (Py_Py3kWarningFlag && PyErr_Warn(PyExc_DeprecationWarning,
+				"dict inequality comparisons not supported in 3.x.") < 0) {
+			return NULL;
+		}
 		res = Py_NotImplemented;
+	}
 	Py_INCREF(res);
 	return res;
  }
diff --git a/Objects/object.c b/Objects/object.c
index 698ba47..a10ac7c 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -863,8 +863,18 @@
 	int c;
 
 	c = try_3way_compare(v, w);
-	if (c >= 2)
+	if (c >= 2) {
+
+		/* Py3K warning if types are not equal and comparison isn't == or !=  */
+		if (Py_Py3kWarningFlag &&
+			v->ob_type != w->ob_type && op != Py_EQ && op != Py_NE &&
+			PyErr_Warn(PyExc_DeprecationWarning,
+				"comparing unequal types not supported in 3.x.") < 0) {
+			return NULL;
+		}
+
 		c = default_3way_compare(v, w);
+	}
 	if (c <= -2)
 		return NULL;
 	return convert_3way_to_object(op, c);
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 7db6dac..82ced39 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -593,6 +593,48 @@
 	return (vv < ww) ? -1 : (vv > ww) ? 1 : 0;
 }
 
+static PyObject*
+type_richcompare(PyObject *v, PyObject *w, int op)
+{
+	PyObject *result;
+	Py_uintptr_t vv, ww;
+	int c;
+
+	/* Make sure both arguments are types. */
+	if (!PyType_Check(v) || !PyType_Check(w)) {
+		result = Py_NotImplemented;
+		goto out;
+	}
+
+	/* Py3K warning if comparison isn't == or !=  */
+	if (Py_Py3kWarningFlag && op != Py_EQ && op != Py_NE &&
+		PyErr_Warn(PyExc_DeprecationWarning,
+			"type inequality comparisons not supported in 3.x.") < 0) {
+		return NULL;
+	}
+
+	/* Compare addresses */
+	vv = (Py_uintptr_t)v;
+	ww = (Py_uintptr_t)w;
+	switch (op) {
+	case Py_LT: c = vv <  ww; break;
+	case Py_LE: c = vv <= ww; break;
+	case Py_EQ: c = vv == ww; break;
+	case Py_NE: c = vv != ww; break;
+	case Py_GT: c = vv >  ww; break;
+	case Py_GE: c = vv >= ww; break;
+	default:
+		result = Py_NotImplemented;
+		goto out;
+	}
+	result = c ? Py_True : Py_False;
+
+  /* incref and return */
+  out:
+	Py_INCREF(result);
+	return result;
+}
+
 static PyObject *
 type_repr(PyTypeObject *type)
 {
@@ -2666,7 +2708,7 @@
 	type_doc,				/* tp_doc */
 	(traverseproc)type_traverse,		/* tp_traverse */
 	(inquiry)type_clear,			/* tp_clear */
-	0,					/* tp_richcompare */
+	type_richcompare,					/* tp_richcompare */
 	offsetof(PyTypeObject, tp_weaklist),	/* tp_weaklistoffset */
 	0,					/* tp_iter */
 	0,					/* tp_iternext */