Index: Parser/asdl_c.py
===================================================================
--- Parser/asdl_c.py    (revision 66834)
+++ Parser/asdl_c.py    (working copy)
@@ -824,12 +824,27 @@
     return 0;
 }
 
+static int add_ast_fields()
+{
+    PyObject *empty_tuple, *d;
+    if (PyType_Ready(&AST_type) < 0)
+        return -1;
+    d = AST_type.tp_dict;
+    empty_tuple = PyTuple_New(0);
+    if (!empty_tuple ||
+        PyDict_SetItemString(d, "_fields", empty_tuple) < 0 ||
+        PyDict_SetItemString(d, "_attributes", empty_tuple) < 0)
+        return -1;
+    return 0;
+}
+
 """, 0, reflow=False)
 
         self.emit("static int init_types(void)",0)
         self.emit("{", 0)
         self.emit("static int initialized;", 1)
         self.emit("if (initialized) return 1;", 1)
+        self.emit("if (add_ast_fields() < 0) return 0;", 1)
         for dfn in mod.dfns:
             self.visit(dfn)
         self.emit("initialized = 1;", 1)