diff --git a/api/v1/swagger/definitions/hold.json b/api/v1/swagger/definitions/hold.json
index f1110f21c3..5f4131860d 100644
--- a/api/v1/swagger/definitions/hold.json
+++ b/api/v1/swagger/definitions/hold.json
@@ -43,7 +43,7 @@
       "description": "a one letter code defining what the status of the hold is after it has been confirmed"
     },
     "timestamp": {
-      "type": "string",
+      "type": ["string", "null"],
       "description": "date and time the hold was last updated"
     },
     "itemnumber": {