diff --git a/packages/hydrooj/src/handler/contest.ts b/packages/hydrooj/src/handler/contest.ts
index 6988d2ebd..04d81c2b9 100644
--- a/packages/hydrooj/src/handler/contest.ts
+++ b/packages/hydrooj/src/handler/contest.ts
@@ -7,7 +7,6 @@ import {
     ContestNotLiveError, ValidationError, ProblemNotFoundError,
     ContestNotAttendedError, PermissionError, BadRequestError,
     ContestNotFoundError, InvalidTokenError, RecordNotFoundError,
-    NotFoundError,
 } from '../error';
 import { ProblemDoc, Tdoc, User } from '../interface';
 import paginate from '../lib/paginate';
diff --git a/packages/hydrooj/src/handler/homework.ts b/packages/hydrooj/src/handler/homework.ts
index 3a8819f42..5dfa00bd3 100644
--- a/packages/hydrooj/src/handler/homework.ts
+++ b/packages/hydrooj/src/handler/homework.ts
@@ -6,7 +6,7 @@ import { Time } from '@hydrooj/utils/lib/utils';
 import { lookup } from 'mime-types';
 import {
     ValidationError, HomeworkNotLiveError, ProblemNotFoundError,
-    HomeworkNotAttendedError, BadRequestError, NotFoundError,
+    HomeworkNotAttendedError, BadRequestError,
 } from '../error';
 import {
     PenaltyRules, Tdoc, ProblemDoc, User,
diff --git a/packages/hydrooj/src/handler/misc.ts b/packages/hydrooj/src/handler/misc.ts
index 45343fea4..ad6cae9b3 100644
--- a/packages/hydrooj/src/handler/misc.ts
+++ b/packages/hydrooj/src/handler/misc.ts
@@ -2,8 +2,7 @@
 import { pick } from 'lodash';
 import { lookup } from 'mime-types';
 import {
-    BadRequestError, ForbiddenError, NotFoundError,
-    ValidationError,
+    BadRequestError, ForbiddenError, ValidationError,
 } from '../error';
 import { sortFiles } from '../utils';
 import { PRIV } from '../model/builtin';
diff --git a/packages/hydrooj/src/handler/problem.ts b/packages/hydrooj/src/handler/problem.ts
index bfead48bc..3b734e76e 100644
--- a/packages/hydrooj/src/handler/problem.ts
+++ b/packages/hydrooj/src/handler/problem.ts
@@ -6,7 +6,7 @@ import { lookup } from 'mime-types';
 import {
     NoProblemError, PermissionError, ValidationError,
     SolutionNotFoundError, ProblemNotFoundError, BadRequestError,
-    ForbiddenError, NotFoundError,
+    ForbiddenError,
 } from '../error';
 import {
     ProblemDoc, User, ProblemStatusDoc,