diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index 301a2d2..0b43549 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -4647,9 +4647,11 @@
     def test_mixing_slot_wrappers(self):
         class X(dict):
             __setattr__ = dict.__setitem__
+            __neg__ = dict.copy
         x = X()
         x.y = 42
         self.assertEqual(x["y"], 42)
+        self.assertEqual(x, -x)
 
     def test_slot_shadows_class_variable(self):
         with self.assertRaises(ValueError) as cm:
diff --git a/Misc/NEWS.d/next/Core and Builtins/2019-06-06-13-59-52.bpo-36922.EMZ3TF.rst b/Misc/NEWS.d/next/Core and Builtins/2019-06-06-13-59-52.bpo-36922.EMZ3TF.rst
new file mode 100644
index 0000000..c2a2ad4
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2019-06-06-13-59-52.bpo-36922.EMZ3TF.rst
@@ -0,0 +1 @@
+Slot functions optimize any callable with ``Py_TPFLAGS_METHOD_DESCRIPTOR`` instead of only instances of ``function``.
\ No newline at end of file
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index ba128a9..e495251 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1412,7 +1412,7 @@
         return NULL;
     }
 
-    if (PyFunction_Check(res)) {
+    if (PyType_HasFeature(Py_TYPE(res), Py_TPFLAGS_METHOD_DESCRIPTOR)) {
         /* Avoid temporary PyMethodObject */
         *unbound = 1;
         Py_INCREF(res);