/** * Prepare value for save * * @param mixed $value * @param Mage_Eav_Model_Entity_Attribute_Abstract $attribute * @return mixed */ protected function _prepareValueForSave($value, Mage_Eav_Model_Entity_Attribute_Abstract $attribute) { $type = $attribute->getBackendType(); if (($type == 'int' || $type == 'decimal' || $type == 'datetime') && $value === '') { $value = null; } return parent::_prepareValueForSave($value, $attribute); }