diff --git a/packages/hydrooj/src/entry/cli.ts b/packages/hydrooj/src/entry/cli.ts
index 12f9cd707..20f8056f4 100644
--- a/packages/hydrooj/src/entry/cli.ts
+++ b/packages/hydrooj/src/entry/cli.ts
@@ -95,7 +95,6 @@ export async function load() {
     await lib(pending, fail);
     const systemModel = require('../model/system');
     await systemModel.runConfig();
-    require('../service/gridfs');
     await service(pending, fail);
     for (const i of builtinModel) require(`../model/${i}`);
     await model(pending, fail);
diff --git a/packages/hydrooj/src/entry/worker.ts b/packages/hydrooj/src/entry/worker.ts
index 3bf4c2619..53a226617 100644
--- a/packages/hydrooj/src/entry/worker.ts
+++ b/packages/hydrooj/src/entry/worker.ts
@@ -50,9 +50,8 @@ export async function load() {
     if (detail) logger.info('finish: lib.builtin');
     await lib(pending, fail);
     if (detail) logger.info('finish: lib.extra');
-    require('../service/gridfs');
     require('../service/monitor');
-    if (detail) logger.info('finish: gridfs/monitor');
+    if (detail) logger.info('finish: monitor');
     const server = require('../service/server');
     await server.prepare();
     if (detail) logger.info('finish: server');
diff --git a/packages/hydrooj/src/service/gridfs.ts b/packages/hydrooj/src/service/gridfs.ts
deleted file mode 100644
index cae1012fe..000000000
--- a/packages/hydrooj/src/service/gridfs.ts
+++ /dev/null
@@ -1,10 +0,0 @@
-import { GridFSBucket } from 'mongodb';
-import db from './db';
-import { HydroFileSystem } from '../interface';
-
-const fs = new GridFSBucket(db.db2);
-
-// @ts-ignore
-global.Hydro.service.fs = fs;
-
-export = fs as HydroFileSystem;
diff --git a/packages/hydrooj/src/upgrade.ts b/packages/hydrooj/src/upgrade.ts
index 62c306906..2d6ae60e2 100644
--- a/packages/hydrooj/src/upgrade.ts
+++ b/packages/hydrooj/src/upgrade.ts
@@ -1,6 +1,6 @@
 /* eslint-disable @typescript-eslint/no-unused-vars */
 /* eslint-disable no-await-in-loop */
-import { ObjectID } from 'mongodb';
+import { ObjectID, GridFSBucket } from 'mongodb';
 import AdmZip from 'adm-zip';
 import Queue from 'p-queue';
 import yaml from 'js-yaml';
@@ -8,15 +8,14 @@ import { pick } from 'lodash';
 import { convertIniConfig } from '@hydrooj/utils/lib/cases';
 import { BucketItem } from 'minio';
 import moment from 'moment';
+import db from './service/db';
 import { Progress } from './ui';
 import { Logger } from './logger';
 import { streamToBuffer } from './utils';
 import {
     iterateAllDomain, iterateAllProblem, iterateAllPsdoc, iterateAllUser,
 } from './pipelineUtils';
-import gridfs from './service/gridfs';
 import storage from './service/storage';
-import db from './service/db';
 import difficultyAlgorithm from './lib/difficulty';
 import problem from './model/problem';
 import user from './model/user';
@@ -81,6 +80,7 @@ const scripts: UpgradeScript[] = [
         else savedProgress = { pdocs: [] };
         const ddocs = await domain.getMulti().project({ _id: 1 }).toArray();
         logger.info('Found %d domains.', ddocs.length);
+        const gridfs = new GridFSBucket(db.db2);
         for (let i = 0; i < ddocs.length; i++) {
             const ddoc = ddocs[i];
             logger.info('Domain %s (%d/%d)', ddoc._id, i + 1, ddocs.length);