diff --git a/src/remote/activitypub/kernel/follow.ts b/src/remote/activitypub/kernel/follow.ts
index 6a8b5a1be..7e31eb32e 100644
--- a/src/remote/activitypub/kernel/follow.ts
+++ b/src/remote/activitypub/kernel/follow.ts
@@ -1,3 +1,4 @@
+import * as mongo from 'mongodb';
 import User, { IRemoteUser } from '../../../models/user';
 import config from '../../../config';
 import follow from '../../../services/following/create';
@@ -10,7 +11,9 @@ export default async (actor: IRemoteUser, activity: IFollow): Promise<void> => {
 		return null;
 	}
 
-	const followee = await User.findOne({ _id: id.split('/').pop() });
+	const followee = await User.findOne({
+		_id: new mongo.ObjectID(id.split('/').pop())
+	});
 
 	if (followee === null) {
 		throw new Error('followee not found');
diff --git a/src/remote/activitypub/kernel/like.ts b/src/remote/activitypub/kernel/like.ts
index 494160858..fc5d0a2f6 100644
--- a/src/remote/activitypub/kernel/like.ts
+++ b/src/remote/activitypub/kernel/like.ts
@@ -1,3 +1,4 @@
+import * as mongo from 'mongodb';
 import Note from '../../../models/note';
 import { IRemoteUser } from '../../../models/user';
 import { ILike } from '../type';
@@ -9,7 +10,7 @@ export default async (actor: IRemoteUser, activity: ILike) => {
 	// Transform:
 	// https://misskey.ex/notes/xxxx to
 	// xxxx
-	const noteId = id.split('/').pop();
+	const noteId = new mongo.ObjectID(id.split('/').pop());
 
 	const note = await Note.findOne({ _id: noteId });
 	if (note === null) {
diff --git a/src/remote/activitypub/kernel/undo/follow.ts b/src/remote/activitypub/kernel/undo/follow.ts
index a85cb0305..c0b10c189 100644
--- a/src/remote/activitypub/kernel/undo/follow.ts
+++ b/src/remote/activitypub/kernel/undo/follow.ts
@@ -1,3 +1,4 @@
+import * as mongo from 'mongodb';
 import User, { IRemoteUser } from '../../../../models/user';
 import config from '../../../../config';
 import unfollow from '../../../../services/following/delete';
@@ -10,7 +11,9 @@ export default async (actor: IRemoteUser, activity: IFollow): Promise<void> => {
 		return null;
 	}
 
-	const followee = await User.findOne({ _id: id.split('/').pop() });
+	const followee = await User.findOne({
+		_id: new mongo.ObjectID(id.split('/').pop())
+	});
 
 	if (followee === null) {
 		throw new Error('followee not found');