diff --git a/packages/backend/src/server/ActivityPubServerService.ts b/packages/backend/src/server/ActivityPubServerService.ts
index f7e0d744a8..0c3da39dbb 100644
--- a/packages/backend/src/server/ActivityPubServerService.ts
+++ b/packages/backend/src/server/ActivityPubServerService.ts
@@ -3,6 +3,7 @@ import fastifyAccepts from '@fastify/accepts';
 import httpSignature from '@peertube/http-signature';
 import { Brackets, In, IsNull, LessThan, Not } from 'typeorm';
 import accepts from 'accepts';
+import vary from 'vary';
 import { DI } from '@/di-symbols.js';
 import type { FollowingsRepository, NotesRepository, EmojisRepository, NoteReactionsRepository, UserProfilesRepository, UserNotePiningsRepository, UsersRepository } from '@/models/index.js';
 import * as url from '@/misc/prelude/url.js';
@@ -443,6 +444,8 @@ export class ActivityPubServerService {
 
 		// note
 		fastify.get<{ Params: { note: string; } }>('/notes/:note', { constraints: { apOrHtml: 'ap' } }, async (request, reply) => {
+			vary(reply.raw, 'Accept');
+	
 			const note = await this.notesRepository.findOneBy({
 				id: request.params.note,
 				visibility: In(['public', 'home']),
@@ -471,6 +474,8 @@ export class ActivityPubServerService {
 
 		// note activity
 		fastify.get<{ Params: { note: string; } }>('/notes/:note/activity', async (request, reply) => {
+			vary(reply.raw, 'Accept');
+
 			const note = await this.notesRepository.findOneBy({
 				id: request.params.note,
 				userHost: IsNull(),
diff --git a/packages/backend/src/server/web/ClientServerService.ts b/packages/backend/src/server/web/ClientServerService.ts
index c537d9a369..1932f88428 100644
--- a/packages/backend/src/server/web/ClientServerService.ts
+++ b/packages/backend/src/server/web/ClientServerService.ts
@@ -13,6 +13,7 @@ import fastifyStatic from '@fastify/static';
 import fastifyView from '@fastify/view';
 import fastifyCookie from '@fastify/cookie';
 import fastifyProxy from '@fastify/http-proxy';
+import vary from 'vary';
 import type { Config } from '@/config.js';
 import { getNoteSummary } from '@/misc/get-note-summary.js';
 import { DI } from '@/di-symbols.js';
@@ -405,6 +406,8 @@ export class ClientServerService {
 
 		// Note
 		fastify.get<{ Params: { note: string; } }>('/notes/:note', async (request, reply) => {
+			vary(reply.raw, 'Accept');
+
 			const note = await this.notesRepository.findOneBy({
 				id: request.params.note,
 				visibility: In(['public', 'home']),