diff --git a/pysollib/struct_new.py b/pysollib/struct_new.py
index b345f003..292be32b 100644
--- a/pysollib/struct_new.py
+++ b/pysollib/struct_new.py
@@ -17,3 +17,9 @@ class NewStruct(object):
         ret = self.__class__()
         ret.__dict__.update(self.__dict__)
         return ret
+
+    def addattr(self, **kw):
+        for k in kw.keys():
+            if k in self.__dict__:
+                raise AttributeError(k)
+        self.__dict__.update(kw)
diff --git a/tests/lib/pysol_tests/game_drag.py b/tests/lib/pysol_tests/game_drag.py
index ec976232..a5a833b9 100644
--- a/tests/lib/pysol_tests/game_drag.py
+++ b/tests/lib/pysol_tests/game_drag.py
@@ -2,7 +2,7 @@
 
 import unittest
 
-from pysollib.game import GameDrag
+from pysollib.game import GameDrag, GameStacks
 
 
 class MyTests(unittest.TestCase):
@@ -10,3 +10,9 @@ class MyTests(unittest.TestCase):
         d = GameDrag()
         d.shadows.append("test")
         self.assertTrue(len(d.shadows))
+
+    def test_addattr(self):
+        s = GameStacks()
+        s.addattr(tableaux=[])
+        s.tableaux.append("myval")
+        self.assertEqual(s.tableaux, ["myval"])