diff --git a/package.json b/package.json
index cae719d02b..19bdc049f6 100644
--- a/package.json
+++ b/package.json
@@ -160,7 +160,7 @@
 		"mkdirp": "0.5.1",
 		"mocha": "5.2.0",
 		"moji": "0.5.1",
-		"mongodb": "3.1.1",
+		"mongodb": "3.1.8",
 		"monk": "6.0.6",
 		"ms": "2.1.1",
 		"nan": "2.11.1",
diff --git a/src/misc/cafy-id.ts b/src/misc/cafy-id.ts
index f3e1f5251b..3880f0bd0c 100644
--- a/src/misc/cafy-id.ts
+++ b/src/misc/cafy-id.ts
@@ -1,5 +1,6 @@
 import * as mongo from 'mongodb';
 import { Context } from 'cafy';
+import isObjectId from './is-objectid';
 
 export const isAnId = (x: any) => mongo.ObjectID.isValid(x);
 export const isNotAnId = (x: any) => !isAnId(x);
@@ -12,7 +13,7 @@ export default class ID extends Context<mongo.ObjectID> {
 		super();
 
 		this.transform = v => {
-			if (isAnId(v) && !mongo.ObjectID.prototype.isPrototypeOf(v)) {
+			if (isAnId(v) && !isObjectId(v)) {
 				return new mongo.ObjectID(v);
 			} else {
 				return v;
@@ -20,7 +21,7 @@ export default class ID extends Context<mongo.ObjectID> {
 		};
 
 		this.push(v => {
-			if (!mongo.ObjectID.prototype.isPrototypeOf(v) && isNotAnId(v)) {
+			if (!isObjectId(v) && isNotAnId(v)) {
 				return new Error('must-be-an-id');
 			}
 			return true;
diff --git a/src/misc/is-objectid.ts b/src/misc/is-objectid.ts
new file mode 100644
index 0000000000..8c1aabd568
--- /dev/null
+++ b/src/misc/is-objectid.ts
@@ -0,0 +1,3 @@
+export default function(x: any): boolean {
+	return x.hasOwnProperty('toHexString') || x.hasOwnProperty('_bsontype');
+}
diff --git a/src/misc/should-mute-this-note.ts b/src/misc/should-mute-this-note.ts
index 663e60af6d..b1d29c6a28 100644
--- a/src/misc/should-mute-this-note.ts
+++ b/src/misc/should-mute-this-note.ts
@@ -1,7 +1,8 @@
 import * as mongo from 'mongodb';
+import isObjectId from './is-objectid';
 
 function toString(id: any) {
-	return mongo.ObjectID.prototype.isPrototypeOf(id) ? (id as mongo.ObjectID).toHexString() : id;
+	return isObjectId(id) ? (id as mongo.ObjectID).toHexString() : id;
 }
 
 export default function(note: any, mutedUserIds: string[]): boolean {
diff --git a/src/models/access-token.ts b/src/models/access-token.ts
index 9909ea01ad..e9cbec7061 100644
--- a/src/models/access-token.ts
+++ b/src/models/access-token.ts
@@ -1,5 +1,6 @@
 import * as mongo from 'mongodb';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 
 const AccessToken = db.get<IAccessToken>('accessTokens');
 AccessToken.createIndex('token');
@@ -22,7 +23,7 @@ export async function deleteAccessToken(accessToken: string | mongo.ObjectID | I
 	let a: IAccessToken;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(accessToken)) {
+	if (isObjectId(accessToken)) {
 		a = await AccessToken.findOne({
 			_id: accessToken
 		});
diff --git a/src/models/app.ts b/src/models/app.ts
index c0b2b5a0f3..45686fe405 100644
--- a/src/models/app.ts
+++ b/src/models/app.ts
@@ -2,6 +2,7 @@ import * as mongo from 'mongodb';
 const deepcopy = require('deepcopy');
 import AccessToken from './access-token';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 import config from '../config';
 
 const App = db.get<IApp>('apps');
@@ -43,7 +44,7 @@ export const pack = (
 	let _app: any;
 
 	// Populate the app if 'app' is ID
-	if (mongo.ObjectID.prototype.isPrototypeOf(app)) {
+	if (isObjectId(app)) {
 		_app = await App.findOne({
 			_id: app
 		});
@@ -56,7 +57,7 @@ export const pack = (
 	}
 
 	// Me
-	if (me && !mongo.ObjectID.prototype.isPrototypeOf(me)) {
+	if (me && !isObjectId(me)) {
 		if (typeof me === 'string') {
 			me = new mongo.ObjectID(me);
 		} else {
diff --git a/src/models/auth-session.ts b/src/models/auth-session.ts
index 3d2c9ee3c1..3458d5675f 100644
--- a/src/models/auth-session.ts
+++ b/src/models/auth-session.ts
@@ -1,6 +1,7 @@
 import * as mongo from 'mongodb';
 const deepcopy = require('deepcopy');
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 import { pack as packApp } from './app';
 
 const AuthSession = db.get<IAuthSession>('authSessions');
@@ -31,7 +32,7 @@ export const pack = (
 	_session = deepcopy(session);
 
 	// Me
-	if (me && !mongo.ObjectID.prototype.isPrototypeOf(me)) {
+	if (me && !isObjectId(me)) {
 		if (typeof me === 'string') {
 			me = new mongo.ObjectID(me);
 		} else {
diff --git a/src/models/drive-file-thumbnail.ts b/src/models/drive-file-thumbnail.ts
index 46de24379f..5864b8d321 100644
--- a/src/models/drive-file-thumbnail.ts
+++ b/src/models/drive-file-thumbnail.ts
@@ -1,5 +1,6 @@
 import * as mongo from 'mongodb';
 import monkDb, { nativeDbConn } from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 
 const DriveFileThumbnail = monkDb.get<IDriveFileThumbnail>('driveFileThumbnails.files');
 DriveFileThumbnail.createIndex('metadata.originalId', { sparse: true, unique: true });
@@ -35,7 +36,7 @@ export async function deleteDriveFileThumbnail(driveFile: string | mongo.ObjectI
 	let d: IDriveFileThumbnail;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(driveFile)) {
+	if (isObjectId(driveFile)) {
 		d = await DriveFileThumbnail.findOne({
 			_id: driveFile
 		});
diff --git a/src/models/drive-file.ts b/src/models/drive-file.ts
index fad6a3ef70..0f81014450 100644
--- a/src/models/drive-file.ts
+++ b/src/models/drive-file.ts
@@ -3,6 +3,7 @@ const deepcopy = require('deepcopy');
 import { pack as packFolder } from './drive-folder';
 import config from '../config';
 import monkDb, { nativeDbConn } from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 import Note, { deleteNote } from './note';
 import MessagingMessage, { deleteMessagingMessage } from './messaging-message';
 import User from './user';
@@ -78,7 +79,7 @@ export async function deleteDriveFile(driveFile: string | mongo.ObjectID | IDriv
 	let d: IDriveFile;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(driveFile)) {
+	if (isObjectId(driveFile)) {
 		d = await DriveFile.findOne({
 			_id: driveFile
 		});
@@ -154,7 +155,7 @@ export const pack = (
 	let _file: any;
 
 	// Populate the file if 'file' is ID
-	if (mongo.ObjectID.prototype.isPrototypeOf(file)) {
+	if (isObjectId(file)) {
 		_file = await DriveFile.findOne({
 			_id: file
 		});
diff --git a/src/models/drive-folder.ts b/src/models/drive-folder.ts
index 4270157694..e826d78403 100644
--- a/src/models/drive-folder.ts
+++ b/src/models/drive-folder.ts
@@ -1,6 +1,7 @@
 import * as mongo from 'mongodb';
 const deepcopy = require('deepcopy');
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 import DriveFile from './drive-file';
 
 const DriveFolder = db.get<IDriveFolder>('driveFolders');
@@ -29,7 +30,7 @@ export async function deleteDriveFolder(driveFolder: string | mongo.ObjectID | I
 	let d: IDriveFolder;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(driveFolder)) {
+	if (isObjectId(driveFolder)) {
 		d = await DriveFolder.findOne({
 			_id: driveFolder
 		});
@@ -83,7 +84,7 @@ export const pack = (
 	let _folder: any;
 
 	// Populate the folder if 'folder' is ID
-	if (mongo.ObjectID.prototype.isPrototypeOf(folder)) {
+	if (isObjectId(folder)) {
 		_folder = await DriveFolder.findOne({ _id: folder });
 	} else if (typeof folder === 'string') {
 		_folder = await DriveFolder.findOne({ _id: new mongo.ObjectID(folder) });
diff --git a/src/models/favorite.ts b/src/models/favorite.ts
index 9acaec5c59..9a01d3a990 100644
--- a/src/models/favorite.ts
+++ b/src/models/favorite.ts
@@ -1,6 +1,7 @@
 import * as mongo from 'mongodb';
 const deepcopy = require('deepcopy');
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 import { pack as packNote } from './note';
 
 const Favorite = db.get<IFavorite>('favorites');
@@ -21,7 +22,7 @@ export async function deleteFavorite(favorite: string | mongo.ObjectID | IFavori
 	let f: IFavorite;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(favorite)) {
+	if (isObjectId(favorite)) {
 		f = await Favorite.findOne({
 			_id: favorite
 		});
@@ -58,7 +59,7 @@ export const pack = (
 	let _favorite: any;
 
 	// Populate the favorite if 'favorite' is ID
-	if (mongo.ObjectID.prototype.isPrototypeOf(favorite)) {
+	if (isObjectId(favorite)) {
 		_favorite = await Favorite.findOne({
 			_id: favorite
 		});
diff --git a/src/models/follow-request.ts b/src/models/follow-request.ts
index b84fc5f5f5..01d4b8ce6b 100644
--- a/src/models/follow-request.ts
+++ b/src/models/follow-request.ts
@@ -1,6 +1,7 @@
 import * as mongo from 'mongodb';
 const deepcopy = require('deepcopy');
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 import { pack as packUser } from './user';
 
 const FollowRequest = db.get<IFollowRequest>('followRequests');
@@ -34,7 +35,7 @@ export async function deleteFollowRequest(followRequest: string | mongo.ObjectID
 	let f: IFollowRequest;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(followRequest)) {
+	if (isObjectId(followRequest)) {
 		f = await FollowRequest.findOne({
 			_id: followRequest
 		});
@@ -64,7 +65,7 @@ export const pack = (
 	let _request: any;
 
 	// Populate the request if 'request' is ID
-	if (mongo.ObjectID.prototype.isPrototypeOf(request)) {
+	if (isObjectId(request)) {
 		_request = await FollowRequest.findOne({
 			_id: request
 		});
diff --git a/src/models/followed-log.ts b/src/models/followed-log.ts
index 7d488b9cd3..0c8c15f118 100644
--- a/src/models/followed-log.ts
+++ b/src/models/followed-log.ts
@@ -1,5 +1,6 @@
 import * as mongo from 'mongodb';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 
 const FollowedLog = db.get<IFollowedLog>('followedLogs');
 export default FollowedLog;
@@ -18,7 +19,7 @@ export async function deleteFollowedLog(followedLog: string | mongo.ObjectID | I
 	let f: IFollowedLog;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(followedLog)) {
+	if (isObjectId(followedLog)) {
 		f = await FollowedLog.findOne({
 			_id: followedLog
 		});
diff --git a/src/models/following-log.ts b/src/models/following-log.ts
index c06a337fd4..d2efb45b3d 100644
--- a/src/models/following-log.ts
+++ b/src/models/following-log.ts
@@ -1,5 +1,6 @@
 import * as mongo from 'mongodb';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 
 const FollowingLog = db.get<IFollowingLog>('followingLogs');
 export default FollowingLog;
@@ -18,7 +19,7 @@ export async function deleteFollowingLog(followingLog: string | mongo.ObjectID |
 	let f: IFollowingLog;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(followingLog)) {
+	if (isObjectId(followingLog)) {
 		f = await FollowingLog.findOne({
 			_id: followingLog
 		});
diff --git a/src/models/following.ts b/src/models/following.ts
index 8aa588f557..2d55ce3616 100644
--- a/src/models/following.ts
+++ b/src/models/following.ts
@@ -1,5 +1,6 @@
 import * as mongo from 'mongodb';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 
 const Following = db.get<IFollowing>('following');
 Following.createIndex(['followerId', 'followeeId'], { unique: true });
@@ -32,7 +33,7 @@ export async function deleteFollowing(following: string | mongo.ObjectID | IFoll
 	let f: IFollowing;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(following)) {
+	if (isObjectId(following)) {
 		f = await Following.findOne({
 			_id: following
 		});
diff --git a/src/models/games/reversi/game.ts b/src/models/games/reversi/game.ts
index 6a6c6463d9..3393932af8 100644
--- a/src/models/games/reversi/game.ts
+++ b/src/models/games/reversi/game.ts
@@ -1,6 +1,7 @@
 import * as mongo from 'mongodb';
 const deepcopy = require('deepcopy');
 import db from '../../../db/mongodb';
+import isObjectId from '../../../misc/is-objectid';
 import { IUser, pack as packUser } from '../../user';
 
 const ReversiGame = db.get<IReversiGame>('reversiGames');
@@ -62,7 +63,7 @@ export const pack = (
 	let _game: any;
 
 	// Populate the game if 'game' is ID
-	if (mongo.ObjectID.prototype.isPrototypeOf(game)) {
+	if (isObjectId(game)) {
 		_game = await ReversiGame.findOne({
 			_id: game
 		});
@@ -76,7 +77,7 @@ export const pack = (
 
 	// Me
 	const meId: mongo.ObjectID = me
-		? mongo.ObjectID.prototype.isPrototypeOf(me)
+		? isObjectId(me)
 			? me as mongo.ObjectID
 			: typeof me === 'string'
 				? new mongo.ObjectID(me)
diff --git a/src/models/games/reversi/matching.ts b/src/models/games/reversi/matching.ts
index e94b832cb0..981665ca2c 100644
--- a/src/models/games/reversi/matching.ts
+++ b/src/models/games/reversi/matching.ts
@@ -1,6 +1,7 @@
 import * as mongo from 'mongodb';
 const deepcopy = require('deepcopy');
 import db from '../../../db/mongodb';
+import isObjectId from '../../../misc/is-objectid';
 import { IUser, pack as packUser } from '../../user';
 
 const Matching = db.get<IMatching>('reversiMatchings');
@@ -23,7 +24,7 @@ export const pack = (
 
 	// Me
 	const meId: mongo.ObjectID = me
-		? mongo.ObjectID.prototype.isPrototypeOf(me)
+		? isObjectId(me)
 			? me as mongo.ObjectID
 			: typeof me === 'string'
 				? new mongo.ObjectID(me)
diff --git a/src/models/messaging-history.ts b/src/models/messaging-history.ts
index 5367f81412..4d7db5617a 100644
--- a/src/models/messaging-history.ts
+++ b/src/models/messaging-history.ts
@@ -1,5 +1,6 @@
 import * as mongo from 'mongodb';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 
 const MessagingHistory = db.get<IMessagingHistory>('messagingHistories');
 export default MessagingHistory;
@@ -19,7 +20,7 @@ export async function deleteMessagingHistory(messagingHistory: string | mongo.Ob
 	let m: IMessagingHistory;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(messagingHistory)) {
+	if (isObjectId(messagingHistory)) {
 		m = await MessagingHistory.findOne({
 			_id: messagingHistory
 		});
diff --git a/src/models/messaging-message.ts b/src/models/messaging-message.ts
index d778164de0..7e94205ca5 100644
--- a/src/models/messaging-message.ts
+++ b/src/models/messaging-message.ts
@@ -3,6 +3,7 @@ const deepcopy = require('deepcopy');
 import { pack as packUser } from './user';
 import { pack as packFile } from './drive-file';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 import MessagingHistory, { deleteMessagingHistory } from './messaging-history';
 import { length } from 'stringz';
 
@@ -30,7 +31,7 @@ export async function deleteMessagingMessage(messagingMessage: string | mongo.Ob
 	let m: IMessagingMessage;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(messagingMessage)) {
+	if (isObjectId(messagingMessage)) {
 		m = await MessagingMessage.findOne({
 			_id: messagingMessage
 		});
@@ -72,7 +73,7 @@ export const pack = (
 	let _message: any;
 
 	// Populate the message if 'message' is ID
-	if (mongo.ObjectID.prototype.isPrototypeOf(message)) {
+	if (isObjectId(message)) {
 		_message = await MessagingMessage.findOne({
 			_id: message
 		});
diff --git a/src/models/mute.ts b/src/models/mute.ts
index 8fe4eb2ee9..adcaf04b36 100644
--- a/src/models/mute.ts
+++ b/src/models/mute.ts
@@ -1,5 +1,6 @@
 import * as mongo from 'mongodb';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 
 const Mute = db.get<IMute>('mute');
 Mute.createIndex(['muterId', 'muteeId'], { unique: true });
@@ -19,7 +20,7 @@ export async function deleteMute(mute: string | mongo.ObjectID | IMute) {
 	let m: IMute;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(mute)) {
+	if (isObjectId(mute)) {
 		m = await Mute.findOne({
 			_id: mute
 		});
diff --git a/src/models/note-reaction.ts b/src/models/note-reaction.ts
index a710fef364..cdc859b5a7 100644
--- a/src/models/note-reaction.ts
+++ b/src/models/note-reaction.ts
@@ -2,6 +2,7 @@ import * as mongo from 'mongodb';
 import $ from 'cafy';
 const deepcopy = require('deepcopy');
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 import Reaction from './note-reaction';
 import { pack as packUser } from './user';
 
@@ -37,7 +38,7 @@ export async function deleteNoteReaction(noteReaction: string | mongo.ObjectID |
 	let n: INoteReaction;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(noteReaction)) {
+	if (isObjectId(noteReaction)) {
 		n = await NoteReaction.findOne({
 			_id: noteReaction
 		});
@@ -67,7 +68,7 @@ export const pack = (
 	let _reaction: any;
 
 	// Populate the reaction if 'reaction' is ID
-	if (mongo.ObjectID.prototype.isPrototypeOf(reaction)) {
+	if (isObjectId(reaction)) {
 		_reaction = await Reaction.findOne({
 			_id: reaction
 		});
diff --git a/src/models/note-watching.ts b/src/models/note-watching.ts
index 479f92dd44..ae576907bc 100644
--- a/src/models/note-watching.ts
+++ b/src/models/note-watching.ts
@@ -1,5 +1,6 @@
 import * as mongo from 'mongodb';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 
 const NoteWatching = db.get<INoteWatching>('noteWatching');
 NoteWatching.createIndex(['userId', 'noteId'], { unique: true });
@@ -19,7 +20,7 @@ export async function deleteNoteWatching(noteWatching: string | mongo.ObjectID |
 	let n: INoteWatching;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(noteWatching)) {
+	if (isObjectId(noteWatching)) {
 		n = await NoteWatching.findOne({
 			_id: noteWatching
 		});
diff --git a/src/models/note.ts b/src/models/note.ts
index e6bdbe0b8b..aeec075636 100644
--- a/src/models/note.ts
+++ b/src/models/note.ts
@@ -2,6 +2,7 @@ import * as mongo from 'mongodb';
 const deepcopy = require('deepcopy');
 import rap from '@prezzemolo/rap';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 import { length } from 'stringz';
 import { IUser, pack as packUser } from './user';
 import { pack as packApp } from './app';
@@ -107,7 +108,7 @@ export async function deleteNote(note: string | mongo.ObjectID | INote) {
 	let n: INote;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(note)) {
+	if (isObjectId(note)) {
 		n = await Note.findOne({
 			_id: note
 		});
@@ -259,7 +260,7 @@ export const pack = async (
 
 	// Me
 	const meId: mongo.ObjectID = me
-		? mongo.ObjectID.prototype.isPrototypeOf(me)
+		? isObjectId(me)
 			? me as mongo.ObjectID
 			: typeof me === 'string'
 				? new mongo.ObjectID(me)
@@ -269,7 +270,7 @@ export const pack = async (
 	let _note: any;
 
 	// Populate the note if 'note' is ID
-	if (mongo.ObjectID.prototype.isPrototypeOf(note)) {
+	if (isObjectId(note)) {
 		_note = await Note.findOne({
 			_id: note
 		});
diff --git a/src/models/notification.ts b/src/models/notification.ts
index 9e700104ab..b385a1ed72 100644
--- a/src/models/notification.ts
+++ b/src/models/notification.ts
@@ -1,6 +1,7 @@
 import * as mongo from 'mongodb';
 const deepcopy = require('deepcopy');
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 import { IUser, pack as packUser } from './user';
 import { pack as packNote } from './note';
 
@@ -57,7 +58,7 @@ export async function deleteNotification(notification: string | mongo.ObjectID |
 	let n: INotification;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(notification)) {
+	if (isObjectId(notification)) {
 		n = await Notification.findOne({
 			_id: notification
 		});
@@ -90,7 +91,7 @@ export const pack = (notification: any) => new Promise<any>(async (resolve, reje
 	let _notification: any;
 
 	// Populate the notification if 'notification' is ID
-	if (mongo.ObjectID.prototype.isPrototypeOf(notification)) {
+	if (isObjectId(notification)) {
 		_notification = await Notification.findOne({
 			_id: notification
 		});
diff --git a/src/models/poll-vote.ts b/src/models/poll-vote.ts
index 85c8454ddc..f9faa8124d 100644
--- a/src/models/poll-vote.ts
+++ b/src/models/poll-vote.ts
@@ -1,5 +1,6 @@
 import * as mongo from 'mongodb';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 
 const PollVote = db.get<IPollVote>('pollVotes');
 export default PollVote;
@@ -19,7 +20,7 @@ export async function deletePollVote(pollVote: string | mongo.ObjectID | IPollVo
 	let p: IPollVote;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(pollVote)) {
+	if (isObjectId(pollVote)) {
 		p = await PollVote.findOne({
 			_id: pollVote
 		});
diff --git a/src/models/sw-subscription.ts b/src/models/sw-subscription.ts
index a38edd3a50..baeccc28d5 100644
--- a/src/models/sw-subscription.ts
+++ b/src/models/sw-subscription.ts
@@ -1,5 +1,6 @@
 import * as mongo from 'mongodb';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 
 const SwSubscription = db.get<ISwSubscription>('swSubscriptions');
 export default SwSubscription;
@@ -19,7 +20,7 @@ export async function deleteSwSubscription(swSubscription: string | mongo.Object
 	let s: ISwSubscription;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(swSubscription)) {
+	if (isObjectId(swSubscription)) {
 		s = await SwSubscription.findOne({
 			_id: swSubscription
 		});
diff --git a/src/models/user-list.ts b/src/models/user-list.ts
index 5cfa7e4dfc..9e0be6a944 100644
--- a/src/models/user-list.ts
+++ b/src/models/user-list.ts
@@ -1,6 +1,7 @@
 import * as mongo from 'mongodb';
 const deepcopy = require('deepcopy');
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 
 const UserList = db.get<IUserList>('userList');
 export default UserList;
@@ -20,7 +21,7 @@ export async function deleteUserList(userList: string | mongo.ObjectID | IUserLi
 	let u: IUserList;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(userList)) {
+	if (isObjectId(userList)) {
 		u = await UserList.findOne({
 			_id: userList
 		});
@@ -45,7 +46,7 @@ export const pack = (
 ) => new Promise<any>(async (resolve, reject) => {
 	let _userList: any;
 
-	if (mongo.ObjectID.prototype.isPrototypeOf(userList)) {
+	if (isObjectId(userList)) {
 		_userList = await UserList.findOne({
 			_id: userList
 		});
diff --git a/src/models/user.ts b/src/models/user.ts
index 6ca09ca168..f2afe00d15 100644
--- a/src/models/user.ts
+++ b/src/models/user.ts
@@ -3,6 +3,7 @@ const deepcopy = require('deepcopy');
 const sequential = require('promise-sequential');
 import rap from '@prezzemolo/rap';
 import db from '../db/mongodb';
+import isObjectId from '../misc/is-objectid';
 import Note, { packMany as packNoteMany, deleteNote } from './note';
 import Following, { deleteFollowing } from './following';
 import Mute, { deleteMute } from './mute';
@@ -175,7 +176,7 @@ export async function deleteUser(user: string | mongo.ObjectID | IUser) {
 	let u: IUser;
 
 	// Populate
-	if (mongo.ObjectID.prototype.isPrototypeOf(user)) {
+	if (isObjectId(user)) {
 		u = await User.findOne({
 			_id: user
 		});
@@ -340,7 +341,6 @@ export const pack = (
 		includeHasUnreadNotes?: boolean
 	}
 ) => new Promise<any>(async (resolve, reject) => {
-
 	const opts = Object.assign({
 		detail: false,
 		includeSecrets: false
@@ -358,7 +358,7 @@ export const pack = (
 	};
 
 	// Populate the user if 'user' is ID
-	if (mongo.ObjectID.prototype.isPrototypeOf(user)) {
+	if (isObjectId(user)) {
 		_user = await User.findOne({
 			_id: user
 		}, { fields });
@@ -378,7 +378,7 @@ export const pack = (
 
 	// Me
 	const meId: mongo.ObjectID = me
-		? mongo.ObjectID.prototype.isPrototypeOf(me)
+		? isObjectId(me)
 			? me as mongo.ObjectID
 			: typeof me === 'string'
 				? new mongo.ObjectID(me)
diff --git a/src/server/api/common/read-messaging-message.ts b/src/server/api/common/read-messaging-message.ts
index 075e369832..63080d22a4 100644
--- a/src/server/api/common/read-messaging-message.ts
+++ b/src/server/api/common/read-messaging-message.ts
@@ -1,4 +1,5 @@
 import * as mongo from 'mongodb';
+import isObjectId from '../../../misc/is-objectid';
 import Message from '../../../models/messaging-message';
 import { IMessagingMessage as IMessage } from '../../../models/messaging-message';
 import { publishMainStream } from '../../../stream';
@@ -15,21 +16,21 @@ export default (
 	message: string | string[] | IMessage | IMessage[] | mongo.ObjectID | mongo.ObjectID[]
 ) => new Promise<any>(async (resolve, reject) => {
 
-	const userId = mongo.ObjectID.prototype.isPrototypeOf(user)
+	const userId = isObjectId(user)
 		? user
 		: new mongo.ObjectID(user);
 
-	const otherpartyId = mongo.ObjectID.prototype.isPrototypeOf(otherparty)
+	const otherpartyId = isObjectId(otherparty)
 		? otherparty
 		: new mongo.ObjectID(otherparty);
 
 	const ids: mongo.ObjectID[] = Array.isArray(message)
-		? mongo.ObjectID.prototype.isPrototypeOf(message[0])
+		? isObjectId(message[0])
 			? (message as mongo.ObjectID[])
 			: typeof message[0] === 'string'
 				? (message as string[]).map(m => new mongo.ObjectID(m))
 				: (message as IMessage[]).map(m => m._id)
-		: mongo.ObjectID.prototype.isPrototypeOf(message)
+		: isObjectId(message)
 			? [(message as mongo.ObjectID)]
 			: typeof message === 'string'
 				? [new mongo.ObjectID(message)]
diff --git a/src/server/api/common/read-notification.ts b/src/server/api/common/read-notification.ts
index 2d58ada4ce..27d3f1be32 100644
--- a/src/server/api/common/read-notification.ts
+++ b/src/server/api/common/read-notification.ts
@@ -1,4 +1,5 @@
 import * as mongo from 'mongodb';
+import isObjectId from '../../../misc/is-objectid';
 import { default as Notification, INotification } from '../../../models/notification';
 import { publishMainStream } from '../../../stream';
 import Mute from '../../../models/mute';
@@ -12,17 +13,17 @@ export default (
 	message: string | string[] | INotification | INotification[] | mongo.ObjectID | mongo.ObjectID[]
 ) => new Promise<any>(async (resolve, reject) => {
 
-	const userId = mongo.ObjectID.prototype.isPrototypeOf(user)
+	const userId = isObjectId(user)
 		? user
 		: new mongo.ObjectID(user);
 
 	const ids: mongo.ObjectID[] = Array.isArray(message)
-		? mongo.ObjectID.prototype.isPrototypeOf(message[0])
+		? isObjectId(message[0])
 			? (message as mongo.ObjectID[])
 			: typeof message[0] === 'string'
 				? (message as string[]).map(m => new mongo.ObjectID(m))
 				: (message as INotification[]).map(m => m._id)
-		: mongo.ObjectID.prototype.isPrototypeOf(message)
+		: isObjectId(message)
 			? [(message as mongo.ObjectID)]
 			: typeof message === 'string'
 				? [new mongo.ObjectID(message)]
diff --git a/src/services/note/read.ts b/src/services/note/read.ts
index caf5cf318f..f2c1213363 100644
--- a/src/services/note/read.ts
+++ b/src/services/note/read.ts
@@ -1,4 +1,5 @@
 import * as mongo from 'mongodb';
+import isObjectId from '../../misc/is-objectid';
 import { publishMainStream } from '../../stream';
 import User from '../../models/user';
 import NoteUnread from '../../models/note-unread';
@@ -11,11 +12,11 @@ export default (
 	note: string | mongo.ObjectID
 ) => new Promise<any>(async (resolve, reject) => {
 
-	const userId: mongo.ObjectID = mongo.ObjectID.prototype.isPrototypeOf(user)
+	const userId: mongo.ObjectID = isObjectId(user)
 		? user as mongo.ObjectID
 		: new mongo.ObjectID(user);
 
-	const noteId: mongo.ObjectID = mongo.ObjectID.prototype.isPrototypeOf(note)
+	const noteId: mongo.ObjectID = isObjectId(note)
 		? note as mongo.ObjectID
 		: new mongo.ObjectID(note);