diff --git a/Classes/Domain/Repository/DocumentRepository.php b/Classes/Domain/Repository/DocumentRepository.php
index 08639f860..e0307b63e 100644
--- a/Classes/Domain/Repository/DocumentRepository.php
+++ b/Classes/Domain/Repository/DocumentRepository.php
@@ -412,7 +412,7 @@ public function getTableOfContentsFromDb($uid, $pid, $settings)
                 $queryBuilder->expr()->eq('tx_dlf_structures_join.pid', intval($pid)),
                 $excludeOtherWhere
             )
-            ->addOrderBy('tx_dlf_documents.volume_sorting')
+            ->add('orderBy', 'cast(volume_sorting as UNSIGNED) asc')
             ->addOrderBy('tx_dlf_documents.mets_orderlabel')
             ->execute();
     }
@@ -533,7 +533,7 @@ public function findAllByUids($uids, $checkPartof = false)
                 $queryBuilder->expr()->in('tx_dlf_documents.pid', $this->settings['storagePid']),
                 $exprDocumentMatchesUid
             )
-            ->addOrderBy('tx_dlf_documents.volume_sorting', 'asc')
+            ->add('orderBy', 'cast(volume_sorting as UNSIGNED) asc')
             ->addOrderBy('tx_dlf_documents.mets_orderlabel', 'asc')
             ->execute();