diff -r 784fea019cab Lib/test/test_descr.py
--- a/Lib/test/test_descr.py	Wed Nov 09 18:57:00 2016 -0500
+++ b/Lib/test/test_descr.py	Thu Nov 10 15:00:40 2016 +0800
@@ -1305,6 +1305,13 @@
         else:
             self.fail("shouldn't be allowed to set a.foo")
 
+        class Q:
+            __slots__ = ["__qualname__"]
+        a = Q()
+        self.assertNotHasAttr(a, "__qualname__")
+        a.__qualname__ = "a"
+        self.assertEqual(a.__qualname__, "a")
+
         class C1(W, D):
             __slots__ = []
         a = C1()
diff -r 784fea019cab Objects/typeobject.c
--- a/Objects/typeobject.c	Wed Nov 09 18:57:00 2016 -0500
+++ b/Objects/typeobject.c	Thu Nov 10 15:00:40 2016 +0800
@@ -2444,7 +2444,10 @@
                 goto error;
             }
             PyList_SET_ITEM(newslots, j, tmp);
-            if (PyDict_GetItem(dict, tmp)) {
+            /* CPython inserts __qualname__ into the namespace when creating
+               a class and will be removed below. */
+            if (PyDict_GetItem(dict, tmp) &&
+                _PyUnicode_CompareWithId(tmp, &PyId___qualname__) != 0) {
                 PyErr_Format(PyExc_ValueError,
                              "%R in __slots__ conflicts with class variable",
                              tmp);