diff --git a/src/api/common/add-file-to-drive.ts b/src/api/common/add-file-to-drive.ts
index e1baf0819..a96906d29 100644
--- a/src/api/common/add-file-to-drive.ts
+++ b/src/api/common/add-file-to-drive.ts
@@ -13,13 +13,13 @@ import { Duplex } from 'stream';
 
 const log = debug('misskey:register-drive-file');
 
-const addToGridFS = (name, binary, metadata): Promise<any> => new Promise(async (resolve, reject) => {
+const addToGridFS = (name, binary, type, metadata): Promise<any> => new Promise(async (resolve, reject) => {
 	const dataStream = new Duplex();
 	dataStream.push(binary);
 	dataStream.push(null);
 
 	const bucket = await getGridFSBucket();
-	const writeStream = bucket.openUploadStream(name, { metadata });
+	const writeStream = bucket.openUploadStream(name, { contentType: type, metadata });
 	writeStream.once('finish', (doc) => { resolve(doc); });
 	writeStream.on('error', reject);
 	dataStream.pipe(writeStream);
@@ -144,10 +144,9 @@ export default (
 	}
 
 	// Create DriveFile document
-	const file = await addToGridFS(name, data, {
+	const file = await addToGridFS(name, data, mime, {
 		user_id: user._id,
 		folder_id: folder !== null ? folder._id : null,
-		type: mime,
 		comment: comment,
 		properties: properties
 	});
diff --git a/src/api/serializers/drive-file.ts b/src/api/serializers/drive-file.ts
index 57b74cd97..3b76979a4 100644
--- a/src/api/serializers/drive-file.ts
+++ b/src/api/serializers/drive-file.ts
@@ -48,6 +48,7 @@ export default (
 	_target.id = _file._id;
 	_target.created_at = _file.uploadDate;
 	_target.name = _file.filename;
+	_target.type = _file.contentType;
 
 	_target = Object.assign(_target, _file.metadata);
 
diff --git a/tools/migration/issue_882.js b/tools/migration/issue_882.js
new file mode 100644
index 000000000..67a1551e0
--- /dev/null
+++ b/tools/migration/issue_882.js
@@ -0,0 +1,44 @@
+// for Node.js interpret
+
+const { default: DriveFile } = require('../../built/api/models/drive-file')
+
+const migrate = async (doc) => {
+	const result = await DriveFile.update(doc._id, {
+		$set: {
+			contentType: doc.metadata.type
+		},
+		$unset: {
+			'metadata.type': ''
+		}
+	})
+	return result.ok === 1
+}
+
+async function main() {
+	let i = 0;
+
+	const count = await db.get('drive_files').count({});
+
+	const iterate = async () => {
+		if (i == count) return true;
+		console.log(`${i} / ${count}`);
+		const doc = (await db.get('drive_files').find({}, { limit: 1, skip: i }))[0]
+		const res = await migrate(doc);
+		if (!res) {
+			return false;
+		} else {
+			i++
+			return await iterate();
+		}
+	}
+
+	const res = await iterate();
+
+	if (res) {
+		return 'ok';
+	} else {
+		throw 'something happened';
+	}
+}
+
+main().then(console.dir).catch(console.error)
diff --git a/tools/migration/use-gridfs.js b/tools/migration/use-gridfs.js
index c5883e456..106cbd388 100644
--- a/tools/migration/use-gridfs.js
+++ b/tools/migration/use-gridfs.js
@@ -22,6 +22,7 @@ const migrateToGridFS = async (doc) => {
 	const buffer = doc.data ? doc.data.buffer : Buffer.from([0x00]) // アップロードのバグなのか知らないけどなぜか data が存在しない drive_file ドキュメントがまれにあることがわかったので
 	const created_at = doc.created_at
 	const name = doc.name
+	const type = doc.type
 
 	delete doc._id
 	delete doc.created_at
@@ -29,9 +30,10 @@ const migrateToGridFS = async (doc) => {
 	delete doc.hash
 	delete doc.data
 	delete doc.name
+	delete doc.type
 
 	const bucket = await getGridFSBucket()
-	const added = await writeToGridFS(bucket, buffer, id, name, { metadata: doc })
+	const added = await writeToGridFS(bucket, buffer, id, name, { contentType: type, metadata: doc })
 
 	const result = await DriveFile.update(id, {
 		$set: {