diff --git a/packages/hydrooj/src/model/contest.ts b/packages/hydrooj/src/model/contest.ts
index afaa39db6..e0aea115c 100644
--- a/packages/hydrooj/src/model/contest.ts
+++ b/packages/hydrooj/src/model/contest.ts
@@ -963,10 +963,10 @@ export function getClarification(domainId: string, did: ObjectId) {
     return document.get(domainId, document.TYPE_CONTEST_CLARIFICATION, did);
 }
 
-export function getMultiClarification(domainId: string, tid: ObjectId, owner = 0) {
+export function getMultiClarification(domainId: string, tid: ObjectId, owner?: number) {
     return document.getMulti(
         domainId, document.TYPE_CONTEST_CLARIFICATION,
-        { parentType: document.TYPE_CONTEST, parentId: tid, ...(owner ? { owner: { $in: [owner, 0] } } : {}) },
+        { parentType: document.TYPE_CONTEST, parentId: tid, ...(typeof owner === 'number' ? { owner: { $in: [owner, 0] } } : {}) },
     ).sort('_id', -1).toArray();
 }