diff --git a/core/openapi.json b/core/openapi.json
index 5fed9716c5cfe..7cb48b58f0a4c 100644
--- a/core/openapi.json
+++ b/core/openapi.json
@@ -492,7 +492,8 @@
                     },
                     "completionExpectedAt": {
                         "type": "integer",
-                        "format": "int64"
+                        "format": "int64",
+                        "nullable": true
                     }
                 }
             },