diff --git a/src/app/api/notary/OfficeFolderAnchorsController.ts b/src/app/api/notary/OfficeFolderAnchorsController.ts
index 9c4c7fdf..f0e1c76f 100644
--- a/src/app/api/notary/OfficeFolderAnchorsController.ts
+++ b/src/app/api/notary/OfficeFolderAnchorsController.ts
@@ -22,7 +22,7 @@ const hydrateOfficeFolderAnchor = (data: any): OfficeFolderAnchor =>
 			status: data.transactions[0].status,
 
 			anchor_nb_try: data.transactions[0].anchor_nb_try,
-			tx_id: data.transactions[0].tx_id.toString(),
+			tx_id: data.transactions[0].tx_id?.toString() ?? undefined,
 			tx_link: data.transactions[0].tx_link,
 			tx_hash: data.transactions[0].tx_hash,