diff --git a/src/remote/activitypub/act/create.ts b/src/remote/activitypub/act/create.ts
index f97832a98..80afb61bd 100644
--- a/src/remote/activitypub/act/create.ts
+++ b/src/remote/activitypub/act/create.ts
@@ -1,11 +1,13 @@
 import { JSDOM } from 'jsdom';
+import * as debug from 'debug';
 
 import Resolver from '../resolver';
-import DriveFile from '../../../models/drive-file';
 import Post from '../../../models/post';
 import uploadFromUrl from '../../../api/drive/upload-from-url';
 import createPost from '../../../api/post/create';
 
+const log = debug('misskey:activitypub');
+
 export default async (actor, activity): Promise<void> => {
 	if ('actor' in activity && actor.account.uri !== activity.actor) {
 		throw new Error('invalid actor');
@@ -13,26 +15,20 @@ export default async (actor, activity): Promise<void> => {
 
 	const uri = activity.id || activity;
 
-	try {
-		await Promise.all([
-			DriveFile.findOne({ 'metadata.uri': uri }).then(file => {
-				if (file !== null) {
-					throw new Error();
-				}
-			}, () => {}),
-			Post.findOne({ uri }).then(post => {
-				if (post !== null) {
-					throw new Error();
-				}
-			}, () => {})
-		]);
-	} catch (object) {
-		throw new Error(`already registered: ${uri}`);
-	}
+	log(`Create: ${uri}`);
+
+	// TODO: 同じURIをもつものが既に登録されていないかチェック
 
 	const resolver = new Resolver();
 
-	const object = await resolver.resolve(activity);
+	let object;
+
+	try {
+		object = await resolver.resolve(activity.object);
+	} catch (e) {
+		log(`Resolve failed: ${e}`);
+		throw e;
+	}
 
 	switch (object.type) {
 	case 'Image':
@@ -42,15 +38,22 @@ export default async (actor, activity): Promise<void> => {
 	case 'Note':
 		createNote(object);
 		break;
+
+	default:
+		console.warn(`Unknown type: ${object.type}`);
+		break;
 	}
 
 	///
 
 	async function createImage(image) {
 		if ('attributedTo' in image && actor.account.uri !== image.attributedTo) {
+			log(`invalid image: ${JSON.stringify(image, null, 2)}`);
 			throw new Error('invalid image');
 		}
 
+		log(`Creating the Image: ${uri}`);
+
 		return await uploadFromUrl(image.url, actor);
 	}
 
@@ -59,11 +62,14 @@ export default async (actor, activity): Promise<void> => {
 			('attributedTo' in note && actor.account.uri !== note.attributedTo) ||
 			typeof note.id !== 'string'
 		) {
+			log(`invalid note: ${JSON.stringify(note, null, 2)}`);
 			throw new Error('invalid note');
 		}
 
+		log(`Creating the Note: ${uri}`);
+
 		const media = [];
-		if ('attachment' in note) {
+		if ('attachment' in note && note.attachment != null) {
 			note.attachment.forEach(async media => {
 				const created = await createImage(media);
 				media.push(created);
@@ -71,7 +77,7 @@ export default async (actor, activity): Promise<void> => {
 		}
 
 		let reply = null;
-		if ('inReplyTo' in note) {
+		if ('inReplyTo' in note && note.inReplyTo != null) {
 			const inReplyToPost = await Post.findOne({ uri: note.id || note });
 			if (inReplyToPost) {
 				reply = inReplyToPost;
diff --git a/src/remote/activitypub/act/index.ts b/src/remote/activitypub/act/index.ts
index f22500ace..584022709 100644
--- a/src/remote/activitypub/act/index.ts
+++ b/src/remote/activitypub/act/index.ts
@@ -18,6 +18,10 @@ export default async (actor, activity: IObject): Promise<void> => {
 		await follow(actor, activity);
 		break;
 
+	case 'Accept':
+		// noop
+		break;
+
 	case 'Undo':
 		await undo(actor, activity);
 		break;
diff --git a/src/remote/activitypub/renderer/note.ts b/src/remote/activitypub/renderer/note.ts
index 43531b121..e45b10215 100644
--- a/src/remote/activitypub/renderer/note.ts
+++ b/src/remote/activitypub/renderer/note.ts
@@ -2,11 +2,14 @@ import renderDocument from './document';
 import renderHashtag from './hashtag';
 import config from '../../../config';
 import DriveFile from '../../../models/drive-file';
-import Post from '../../../models/post';
-import User from '../../../models/user';
+import Post, { IPost } from '../../../models/post';
+import User, { IUser } from '../../../models/user';
+
+export default async (user: IUser, post: IPost) => {
+	const promisedFiles = post.mediaIds
+		? DriveFile.find({ _id: { $in: post.mediaIds } })
+		: Promise.resolve([]);
 
-export default async (user, post) => {
-	const promisedFiles = DriveFile.find({ _id: { $in: post.mediaIds } });
 	let inReplyTo;
 
 	if (post.replyId) {
@@ -39,6 +42,6 @@ export default async (user, post) => {
 		cc: `${attributedTo}/followers`,
 		inReplyTo,
 		attachment: (await promisedFiles).map(renderDocument),
-		tag: post.tags.map(renderHashtag)
+		tag: (post.tags || []).map(renderHashtag)
 	};
 };