diff --git a/packages/backend/src/core/MessagingService.ts b/packages/backend/src/core/MessagingService.ts
index cabad96ce7..5891f2c8ea 100644
--- a/packages/backend/src/core/MessagingService.ts
+++ b/packages/backend/src/core/MessagingService.ts
@@ -294,7 +294,7 @@ export class MessagingService {
 				.where('message.groupId = :groupId', { groupId: groupId })
 				.andWhere('message.userId != :userId', { userId: userId })
 				.andWhere('NOT (:userId = ANY(message.reads))', { userId: userId })
-				.andWhere('message.createdAt > :joinedAt', { joinedAt: this.idService.parse(joining.id) }) // 自分が加入する前の会話については、未読扱いしない
+				.andWhere('message.id > :joinedAt', { joinedAt: this.idService.parse(joining.id) }) // 自分が加入する前の会話については、未読扱いしない
 				.getOne().then(x => x != null);
 
 			if (!unreadExist) {
diff --git a/packages/backend/src/core/entities/UserEntityService.ts b/packages/backend/src/core/entities/UserEntityService.ts
index cdee4b9ac7..ad97ffd9d7 100644
--- a/packages/backend/src/core/entities/UserEntityService.ts
+++ b/packages/backend/src/core/entities/UserEntityService.ts
@@ -233,7 +233,7 @@ export class UserEntityService implements OnModuleInit {
 			.where('message.groupId = :groupId', { groupId: j.userGroupId })
 			.andWhere('message.userId != :userId', { userId: userId })
 			.andWhere('NOT (:userId = ANY(message.reads))', { userId: userId })
-			.andWhere('message.createdAt > :joinedAt', { joinedAt: this.idService.parse(j.id) }) // 自分が加入する前の会話については、未読扱いしない
+			.andWhere('message.id > :joinedAt', { joinedAt: this.idService.parse(j.id) }) // 自分が加入する前の会話については、未読扱いしない
 			.getOne().then(x => x != null)));
 
 		const [withUser, withGroups] = await Promise.all([
diff --git a/packages/backend/src/server/api/endpoints/messaging/history.ts b/packages/backend/src/server/api/endpoints/messaging/history.ts
index 83e9e0f783..c314ba46c7 100644
--- a/packages/backend/src/server/api/endpoints/messaging/history.ts
+++ b/packages/backend/src/server/api/endpoints/messaging/history.ts
@@ -73,7 +73,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 					: history.map(m => (m.userId === me.id) ? m.recipientId! : m.userId!);
 
 				const query = this.messagingMessagesRepository.createQueryBuilder('message')
-					.orderBy('message.createdAt', 'DESC');
+					.orderBy('message.id', 'DESC');
 
 				if (ps.group) {
 					query.where('message.groupId IN (:...groups)', { groups: groups });