diff -r ddc95a9bc2e0 Objects/typeobject.c
--- a/Objects/typeobject.c	Wed Sep 07 13:18:40 2016 +0200
+++ b/Objects/typeobject.c	Wed Sep 07 14:50:39 2016 +0300
@@ -455,27 +455,38 @@ type_set_qualname(PyTypeObject *type, Py
 static PyObject *
 type_module(PyTypeObject *type, void *context)
 {
-    char *s;
-
-    if (type->tp_flags & Py_TPFLAGS_HEAPTYPE) {
-        PyObject *mod = _PyDict_GetItemId(type->tp_dict, &PyId___module__);
-        if (!mod) {
-            PyErr_Format(PyExc_AttributeError, "__module__");
-            return 0;
-        }
+    PyObject *mod;
+    const char *s;
+
+    mod = _PyDict_GetItemId(type->tp_dict, &PyId___module__);
+    if (mod != NULL) {
         Py_INCREF(mod);
         return mod;
     }
+    if (type->tp_flags & Py_TPFLAGS_HEAPTYPE) {
+        PyErr_SetString(PyExc_AttributeError, "__module__");
+        return NULL;
+    }
+
+    s = strrchr(type->tp_name, '.');
+    if (s != NULL) {
+        mod = PyUnicode_FromStringAndSize(
+            type->tp_name, (Py_ssize_t)(s - type->tp_name));
+        if (mod == NULL)
+            return NULL;
+        PyUnicode_InternInPlace(&mod);
+        if (type->tp_dict && PyDict_Check(type->tp_dict)) {
+            if (_PyDict_SetItemId(type->tp_dict, &PyId___module__, mod) < 0)
+                PyErr_Clear();
+        }
+        Py_INCREF(mod);
+        return mod;
+    }
     else {
-        PyObject *name;
-        s = strrchr(type->tp_name, '.');
-        if (s != NULL)
-            return PyUnicode_FromStringAndSize(
-                type->tp_name, (Py_ssize_t)(s - type->tp_name));
-        name = _PyUnicode_FromId(&PyId_builtins);
-        Py_XINCREF(name);
-        return name;
-    }
+        mod = _PyUnicode_FromId(&PyId_builtins);
+        Py_XINCREF(mod);
+    }
+    return mod;
 }
 
 static int