diff --git a/api/v1/swagger/definitions/hold.yaml b/api/v1/swagger/definitions/hold.yaml
index 98d4309cca..2ba3367e04 100644
--- a/api/v1/swagger/definitions/hold.yaml
+++ b/api/v1/swagger/definitions/hold.yaml
@@ -17,7 +17,9 @@ properties:
     type: integer
     description: Internal biblio identifier
   deleted_biblio_id:
-    type: integer
+    type:
+      - integer
+      - "null"
     description: Internal deleted biblio identifier
   item_group_id:
     type: