--- src/Eccube/Controller/Admin/Product/ProductController.php.orig      2016-02-17 10:39:43.000000000 +0900
+++ src/Eccube/Controller/Admin/Product/ProductController.php   2016-04-21 10:11:01.722155835 +0900
@@ -291,8 +291,9 @@
                     // ?????
                     $BaseInfo = $app['eccube.repository.base_info']->get();
                     if ($BaseInfo->getOptionProductTaxRule() == Constant::ENABLED) {
-                        if ($ProductClass->getTaxRate()) {
-                            if ($ProductClass->getTaxRule() && !$ProductClass->getTaxRule()->getDelFlg()) {
+                        if ($ProductClass->getTaxRate() !== null) {
+                            if ($ProductClass->getTaxRule()) {
+                                $ProductClass->getTaxRule()->setDelFlg(Constant::DISABLED);
                                 $ProductClass->getTaxRule()->setTaxRate($ProductClass->getTaxRate());
                             } else {
                                 $taxrule = $app['eccube.repository.tax_rule']->newTaxRule();