diff --git a/trytond/model/modelsql.py b/trytond/model/modelsql.py
index 29780da74b..fda2d90a81 100644
--- a/trytond/model/modelsql.py
+++ b/trytond/model/modelsql.py
@@ -312,14 +312,6 @@ class ModelSQL(ModelStorage):
                     values[field]))
             else:
                 upd_todo.append(field)
-            if (isinstance(column, fields.Many2One)
-                    and column.model_name == self._name
-                    and column.left and column.right
-                    and set((column.left, column.right)).isdisjoint(values)):
-                upd0 += ', "%s", "%s"' % (column.left, column.right)
-                upd1 += ', %s, %s'
-                upd2.extend([0, 0])
-
             if field in self._columns \
                     and hasattr(self._columns[field], 'selection') \
                     and self._columns[field].selection \
diff --git a/trytond/test/mptt.py b/trytond/test/mptt.py
index 78cba0fb34..c9bc027521 100644
--- a/trytond/test/mptt.py
+++ b/trytond/test/mptt.py
@@ -30,4 +30,10 @@ class MPTT(ModelSQL, ModelView):
     def default_active(self):
         return True
 
+    def default_left(self):
+        return 0
+
+    def default_right(self):
+        return 0
+
 MPTT()