diff --git a/packages/misskey-js/src/api.ts b/packages/misskey-js/src/api.ts
index fcc9884465..17de317d19 100644
--- a/packages/misskey-js/src/api.ts
+++ b/packages/misskey-js/src/api.ts
@@ -1,4 +1,4 @@
-import type { Endpoints } from './api.types';
+import type { Endpoints } from './api.types.js';
 
 const MK_API_ERROR = Symbol();
 
diff --git a/packages/misskey-js/src/api.types.ts b/packages/misskey-js/src/api.types.ts
index 63f0b77e8d..8659261949 100644
--- a/packages/misskey-js/src/api.types.ts
+++ b/packages/misskey-js/src/api.types.ts
@@ -3,7 +3,7 @@ import type {
 	LiteInstanceMetadata,
 	MeDetailed,
 	Note, NoteFavorite, OriginType, Page, ServerInfo, Stats, User, UserDetailed, UserGroup, UserList, UserSorting, Notification, NoteReaction, Signin, MessagingMessage,
-} from './entities';
+} from './entities.js';
 
 type TODO = Record<string, any> | null;
 
diff --git a/packages/misskey-js/src/index.ts b/packages/misskey-js/src/index.ts
index f431d65cc7..bdd0d04455 100644
--- a/packages/misskey-js/src/index.ts
+++ b/packages/misskey-js/src/index.ts
@@ -1,8 +1,8 @@
-import { Endpoints } from './api.types';
-import Stream, { Connection } from './streaming';
-import { Channels } from './streaming.types';
-import { Acct } from './acct';
-import * as consts from './consts';
+import { Endpoints } from './api.types.js';
+import Stream, { Connection } from './streaming.js';
+import { Channels } from './streaming.types.js';
+import { Acct } from './acct.js';
+import * as consts from './consts.js';
 
 export {
 	Endpoints,
@@ -19,8 +19,8 @@ export const mutedNoteReasons = consts.mutedNoteReasons;
 export const ffVisibility = consts.ffVisibility;
 
 // api extractor not supported yet
-//export * as api from './api';
-//export * as entities from './entities';
-import * as api from './api';
-import * as entities from './entities';
+//export * as api from './api.js';
+//export * as entities from './entities.js';
+import * as api from './api.js';
+import * as entities from './entities.js';
 export { api, entities };
diff --git a/packages/misskey-js/src/streaming.ts b/packages/misskey-js/src/streaming.ts
index 6388828689..9dd764952e 100644
--- a/packages/misskey-js/src/streaming.ts
+++ b/packages/misskey-js/src/streaming.ts
@@ -1,7 +1,7 @@
 import autobind from 'autobind-decorator';
 import { EventEmitter } from 'eventemitter3';
 import ReconnectingWebsocket from 'reconnecting-websocket';
-import type { BroadcastEvents, Channels } from './streaming.types';
+import type { BroadcastEvents, Channels } from './streaming.types.js';
 
 export function urlQuery(obj: Record<string, string | number | boolean | undefined>): string {
 	const params = Object.entries(obj)
diff --git a/packages/misskey-js/src/streaming.types.ts b/packages/misskey-js/src/streaming.types.ts
index d58b90530e..a64545f8e2 100644
--- a/packages/misskey-js/src/streaming.types.ts
+++ b/packages/misskey-js/src/streaming.types.ts
@@ -1,4 +1,4 @@
-import type { Antenna, CustomEmoji, DriveFile, MeDetailed, MessagingMessage, Note, Notification, PageEvent, User, UserGroup } from './entities';
+import type { Antenna, CustomEmoji, DriveFile, MeDetailed, MessagingMessage, Note, Notification, PageEvent, User, UserGroup } from './entities.js';
 
 type FIXME = any;
 
diff --git a/packages/misskey-js/test/api.ts b/packages/misskey-js/test/api.ts
index 47c8378014..84b1fc0933 100644
--- a/packages/misskey-js/test/api.ts
+++ b/packages/misskey-js/test/api.ts
@@ -1,5 +1,5 @@
-import { APIClient, isAPIError } from '../src/api';
 import { enableFetchMocks } from 'jest-fetch-mock';
+import { APIClient, isAPIError } from '../src/api';
 
 enableFetchMocks();