diff --git a/packages/hydrooj/src/model/contest.ts b/packages/hydrooj/src/model/contest.ts
index 7e46f6b5f..c2c5739fc 100644
--- a/packages/hydrooj/src/model/contest.ts
+++ b/packages/hydrooj/src/model/contest.ts
@@ -824,6 +824,7 @@ export async function edit(domainId: string, tid: ObjectId, $set: Partial<Tdoc>)
     if ($set.rule && !RULES[$set.rule]) throw new ValidationError('rule');
     const tdoc = await document.get(domainId, document.TYPE_CONTEST, tid);
     if (!tdoc) throw new ContestNotFoundError(domainId, tid);
+    await bus.parallel('contest/before-edit', tdoc, $set);
     RULES[$set.rule || tdoc.rule].check(Object.assign(tdoc, $set));
     const res = await document.set(domainId, document.TYPE_CONTEST, tid, $set);
     await bus.parallel('contest/edit', res);
diff --git a/packages/hydrooj/src/service/bus.ts b/packages/hydrooj/src/service/bus.ts
index c412fb4fa..d4b425dd9 100644
--- a/packages/hydrooj/src/service/bus.ts
+++ b/packages/hydrooj/src/service/bus.ts
@@ -85,6 +85,7 @@ export interface EventMap {
 
     'contest/before-add': (payload: Partial<Tdoc>) => VoidReturn;
     'contest/add': (payload: Partial<Tdoc>, id: ObjectId) => VoidReturn;
+    'contest/before-edit': (tdoc: Tdoc, $set: Partial<Tdoc>) => VoidReturn;
     'contest/edit': (payload: Tdoc) => VoidReturn;
     'contest/list': (query: Filter<Tdoc>, handler: any) => VoidReturn;
     'contest/scoreboard': (tdoc: Tdoc, rows: ScoreboardRow[], udict: BaseUserDict, pdict: ProblemDict) => VoidReturn;