private function checkBeforeUpdate()
    {
        if (0 <= version_compare(BBApplication::VERSION, '1.1')) {
            $schemaManager = $this->em->getConnection()->getSchemaManager();
            $pageName = $this->em->getClassMetadata('BackBee\NestedNode\Page')->getTableName();
            $sectionName = $this->em->getClassMetadata('BackBee\NestedNode\Section')->getTableName();

            if (false === $schemaManager->tablesExist($sectionName) && true === $schemaManager->tablesExist($pageName)) {
                throw new BBException(sprintf('Table `%s` does not exist. Perhaps you should launch bbapp:upgradeToPageSection command before.', $sectionName));
            }
        }
    }