diff -r 9ded2433dc2c Lib/test/test_subclassinit.py
--- a/Lib/test/test_subclassinit.py	Mon Nov 28 20:56:37 2016 +0200
+++ b/Lib/test/test_subclassinit.py	Tue Nov 29 09:01:48 2016 +0200
@@ -198,6 +198,22 @@ class Test(unittest.TestCase):
         self.assertIs(B.meta_owner, B)
         self.assertEqual(B.name, 'd')
 
+    def test_set_name_mutating_dict(self):
+        notified = []
+        class Descriptor:
+            def __set_name__(self, owner, name):
+                setattr(owner, name + 'x', None)
+                notified.append(name)
+
+        class A:
+            a = Descriptor()
+            b = Descriptor()
+            c = Descriptor()
+            d = Descriptor()
+            e = Descriptor()
+
+        self.assertCountEqual(notified, ['a', 'b', 'c', 'd', 'e'])
+
     def test_errors(self):
         class MyMeta(type):
             pass
diff -r 9ded2433dc2c Objects/typeobject.c
--- a/Objects/typeobject.c	Mon Nov 28 20:56:37 2016 +0200
+++ b/Objects/typeobject.c	Tue Nov 29 09:01:48 2016 +0200
@@ -7004,28 +7004,56 @@ update_all_slots(PyTypeObject* type)
 static int
 set_names(PyTypeObject *type)
 {
-    PyObject *key, *value, *set_name, *tmp;
-    Py_ssize_t i = 0;
-
+    PyObject *names_to_set, *key, *value, *set_name, *tuple, *tmp;
+    Py_ssize_t i;
+
+    names_to_set = PyList_New(0);
+    if (names_to_set == NULL)
+        return -1;
+
+    i = 0;
     while (PyDict_Next(type->tp_dict, &i, &key, &value)) {
         set_name = lookup_maybe(value, &PyId___set_name__);
         if (set_name != NULL) {
-            tmp = PyObject_CallFunctionObjArgs(set_name, type, key, NULL);
+            tuple = PyTuple_Pack(3, set_name, key, value);
             Py_DECREF(set_name);
-            if (tmp == NULL) {
-                _PyErr_FormatFromCause(PyExc_RuntimeError,
-                    "Error calling __set_name__ on '%.100s' instance %R "
-                    "in '%.100s'",
-                    value->ob_type->tp_name, key, type->tp_name);
+            if (tuple == NULL) {
+                Py_DECREF(names_to_set);
                 return -1;
             }
-            else
-                Py_DECREF(tmp);
-        }
-        else if (PyErr_Occurred())
+            if (PyList_Append(names_to_set, tuple) < 0) {
+                Py_DECREF(tuple);
+                Py_DECREF(names_to_set);
+                return -1;
+            }
+            Py_DECREF(tuple);
+        }
+        else if (PyErr_Occurred()) {
+            Py_DECREF(names_to_set);
             return -1;
-    }
-
+        }
+    }
+
+    for (i = 0; i < PyList_GET_SIZE(names_to_set); i++) {
+        tuple = PyList_GET_ITEM(names_to_set, i);
+        assert(PyTuple_CheckExact(tuple));
+        assert(PyTuple_GET_SIZE(tuple) == 3);
+        set_name = PyTuple_GET_ITEM(tuple, 0);
+        key = PyTuple_GET_ITEM(tuple, 1);
+        tmp = PyObject_CallFunctionObjArgs(set_name, type, key, NULL);
+        if (tmp == NULL) {
+            value = PyTuple_GET_ITEM(tuple, 2);
+            _PyErr_FormatFromCause(PyExc_RuntimeError,
+                "Error calling __set_name__ on '%.100s' instance %R "
+                "in '%.100s'",
+                value->ob_type->tp_name, key, type->tp_name);
+            Py_DECREF(names_to_set);
+            return -1;
+        }
+        Py_DECREF(tmp);
+    }
+
+    Py_DECREF(names_to_set);
     return 0;
 }