diff --git a/api/v1/swagger/definitions/account_line.json b/api/v1/swagger/definitions/account_line.json
index 5cdd169518..04c61551f8 100644
--- a/api/v1/swagger/definitions/account_line.json
+++ b/api/v1/swagger/definitions/account_line.json
@@ -84,7 +84,10 @@
       "description": "Internal note"
     },
     "user_id": {
-      "type": "integer",
+      "type": [
+        "integer",
+        "null"
+      ],
       "description": "Internal patron identifier for the staff member that introduced the account line"
     },
     "library_id": {