diff --git a/tests/test_class_sp_trampoline_weak_ptr.cpp b/tests/test_class_sp_trampoline_weak_ptr.cpp
index 4821fd711..06250b303 100644
--- a/tests/test_class_sp_trampoline_weak_ptr.cpp
+++ b/tests/test_class_sp_trampoline_weak_ptr.cpp
@@ -34,6 +34,20 @@ private:
     std::weak_ptr<VirtBase> wp;
 };
 
+struct SpOwner {
+    void set_sp(const std::shared_ptr<VirtBase> &sp) { this->sp = sp; }
+
+    int get_code() {
+        if (!sp) {
+            return -888;
+        }
+        return sp->get_code();
+    }
+
+private:
+    std::shared_ptr<VirtBase> sp;
+};
+
 } // namespace class_sp_trampoline_weak_ptr
 } // namespace pybind11_tests
 
@@ -48,4 +62,9 @@ TEST_SUBMODULE(class_sp_trampoline_weak_ptr, m) {
         .def(py::init<>())
         .def("set_wp", &WpOwner::set_wp)
         .def("get_code", &WpOwner::get_code);
+
+    py::class_<SpOwner>(m, "SpOwner")
+        .def(py::init<>())
+        .def("set_sp", &SpOwner::set_sp)
+        .def("get_code", &SpOwner::get_code);
 }
diff --git a/tests/test_class_sp_trampoline_weak_ptr.py b/tests/test_class_sp_trampoline_weak_ptr.py
index 3782cd8aa..5c427f980 100644
--- a/tests/test_class_sp_trampoline_weak_ptr.py
+++ b/tests/test_class_sp_trampoline_weak_ptr.py
@@ -12,7 +12,7 @@ class PyDrvd(m.VirtBase):
 
 
 @pytest.mark.parametrize(("vtype", "expected_code"), [(m.VirtBase, 100), (PyDrvd, 200)])
-def test_weak_ptr_owner(vtype, expected_code):
+def test_with_wp_owner(vtype, expected_code):
     wpo = m.WpOwner()
     assert wpo.get_code() == -999
 
@@ -26,3 +26,44 @@ def test_weak_ptr_owner(vtype, expected_code):
     if env.PYPY or env.GRAALPY:
         pytest.skip("Cannot reliably trigger GC")
     assert wpo.get_code() == -999
+
+
+@pytest.mark.parametrize(("vtype", "expected_code"), [(m.VirtBase, 100), (PyDrvd, 200)])
+def test_with_sp_owner(vtype, expected_code):
+    spo = m.SpOwner()
+    assert spo.get_code() == -888
+
+    obj = vtype()
+    assert obj.get_code() == expected_code
+
+    spo.set_sp(obj)
+    assert spo.get_code() == expected_code
+
+    del obj
+    if env.PYPY or env.GRAALPY:
+        pytest.skip("Cannot reliably trigger GC")
+    assert spo.get_code() == 100  # Inheritance slicing (issue #1333)
+
+
+@pytest.mark.parametrize(("vtype", "expected_code"), [(m.VirtBase, 100), (PyDrvd, 200)])
+def test_with_sp_and_wp_owners(vtype, expected_code):
+    spo = m.SpOwner()
+    wpo = m.WpOwner()
+
+    obj = vtype()
+    spo.set_sp(obj)
+    wpo.set_wp(obj)
+
+    assert spo.get_code() == expected_code
+    assert wpo.get_code() == expected_code
+
+    del obj
+    if env.PYPY or env.GRAALPY:
+        pytest.skip("Cannot reliably trigger GC")
+
+    # Inheritance slicing (issue #1333)
+    assert spo.get_code() == 100
+    assert wpo.get_code() == 100
+
+    del spo
+    assert wpo.get_code() == -999