Problem with fields in table and writethrough

I generate editable table with TableFieldFactory.

table.setContainerDataSource(container);

        table.setTableFieldFactory(new TableFieldFactory() {
            @Override
            public Field createField(Container container, Object itemId, Object propertyId, Component uiContext) {
                if ("myfield".equals(propertyId)) {

                    Select select = new Select();
                    select.setContainerDataSource(items);
                    select.setPropertyDataSource(container.getContainerProperty(itemId, propertyId));
                    select.setItemCaptionPropertyId("name");
                    select.setNewItemsAllowed(false);
                    select.setWriteThrough(false);
                    select.setImmediate(true);
                    select.setSizeFull();

                    return select;
                }
            }
        });

        view.getRulesTable().setVisibleColumns(new String[] { "myfield"});

Vaadin set "modified=true" attribute to select only after SECOND change. Where the problem? Also Vaadin 6.7.3