diff --git a/server/src/modules/book/book.controller.test.ts b/server/src/modules/book/book.controller.test.ts
index a07130f78..a4085578b 100644
--- a/server/src/modules/book/book.controller.test.ts
+++ b/server/src/modules/book/book.controller.test.ts
@@ -159,13 +159,15 @@ describe('BookController', () => {
 
   it('returns 304 when cover etag matches', async () => {
     const { controller, bookService } = makeController();
-    const { reply } = makeReply();
+    const { reply, headers } = makeReply();
     bookService.getCoverPath.mockResolvedValue('/tmp/cover.jpg');
     mockStat.mockResolvedValue({ mtimeMs: 1234 } as never);
 
     await controller.getCover(7, makeUser(), reply, '"1234"');
 
     expect(reply.status).toHaveBeenCalledWith(304);
+    expect(headers['Cache-Control']).toBe('private, max-age=86400');
+    expect(headers['ETag']).toBe('"1234"');
     expect(reply.send).toHaveBeenCalled();
     expect(mockCreateReadStream).not.toHaveBeenCalled();
   });
@@ -178,7 +180,7 @@ describe('BookController', () => {
 
     await controller.getCover(7, makeUser(), reply, undefined);
 
-    expect(headers['Cache-Control']).toBe('no-cache');
+    expect(headers['Cache-Control']).toBe('private, max-age=86400');
     expect(headers['ETag']).toBe('"4321"');
     expect(reply.type).toHaveBeenCalledWith('image/png');
     expect(mockCreateReadStream).toHaveBeenCalledWith('/tmp/cover.png');
diff --git a/server/src/modules/book/book.controller.ts b/server/src/modules/book/book.controller.ts
index 028d11834..8dd61cca1 100644
--- a/server/src/modules/book/book.controller.ts
+++ b/server/src/modules/book/book.controller.ts
@@ -228,13 +228,13 @@ export class BookController {
     const { mtimeMs } = await stat(coverPath);
     const etag = `"${Math.floor(mtimeMs)}"`;
     if (ifNoneMatch === etag) {
-      reply.status(304).send();
+      reply.status(304).header('Cache-Control', 'private, max-age=86400').header('ETag', etag).send();
       return;
     }
 
     const ext = coverPath.split('.').pop()?.toLowerCase();
     const contentType = ext === 'png' ? 'image/png' : 'image/jpeg';
-    reply.header('Cache-Control', 'no-cache');
+    reply.header('Cache-Control', 'private, max-age=86400');
     reply.header('ETag', etag);
     reply.type(contentType);
     reply.send(createReadStream(coverPath));
@@ -253,11 +253,11 @@ export class BookController {
     const { mtimeMs } = await stat(thumbnailPath);
     const etag = `"${Math.floor(mtimeMs)}"`;
     if (ifNoneMatch === etag) {
-      reply.status(304).send();
+      reply.status(304).header('Cache-Control', 'private, max-age=86400').header('ETag', etag).send();
       return;
     }
 
-    reply.header('Cache-Control', 'no-cache');
+    reply.header('Cache-Control', 'private, max-age=86400');
     reply.header('ETag', etag);
     reply.type('image/jpeg');
     reply.send(createReadStream(thumbnailPath));