diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2efa1b230d..900d042eaf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -22,6 +22,7 @@
 - fix: 「設定のバックアップ」で一部の項目がバックアップに含まれていなかった問題を修正
 
 ### Server
+- Fix: 時間経過により無効化されたアンテナを再有効化したとき、サーバ再起動までその状況が反映されないのを修正 #12303
 - Fix: ロールタイムラインが保存されない問題を修正
 
 ## 2023.11.1
diff --git a/packages/backend/src/core/AntennaService.ts b/packages/backend/src/core/AntennaService.ts
index 65be275548..2815d24734 100644
--- a/packages/backend/src/core/AntennaService.ts
+++ b/packages/backend/src/core/AntennaService.ts
@@ -60,11 +60,21 @@ export class AntennaService implements OnApplicationShutdown {
 						lastUsedAt: new Date(body.lastUsedAt),
 					});
 					break;
-				case 'antennaUpdated':
-					this.antennas[this.antennas.findIndex(a => a.id === body.id)] = {
-						...body,
-						lastUsedAt: new Date(body.lastUsedAt),
-					};
+				case 'antennaUpdated': {
+					const idx = this.antennas.findIndex(a => a.id === body.id);
+					if (idx >= 0) {
+						this.antennas[idx] = {
+							...body,
+							lastUsedAt: new Date(body.lastUsedAt),
+						};
+					} else {
+						// サーバ起動時にactiveじゃなかった場合、リストに持っていないので追加する必要あり
+						this.antennas.push({
+							...body,
+							lastUsedAt: new Date(body.lastUsedAt),
+						});
+					}
+				}
 					break;
 				case 'antennaDeleted':
 					this.antennas = this.antennas.filter(a => a.id !== body.id);
diff --git a/packages/backend/src/server/api/endpoints/antennas/notes.ts b/packages/backend/src/server/api/endpoints/antennas/notes.ts
index 9b5911800c..29e56b1085 100644
--- a/packages/backend/src/server/api/endpoints/antennas/notes.ts
+++ b/packages/backend/src/server/api/endpoints/antennas/notes.ts
@@ -13,6 +13,7 @@ import { DI } from '@/di-symbols.js';
 import { NoteEntityService } from '@/core/entities/NoteEntityService.js';
 import { IdService } from '@/core/IdService.js';
 import { FunoutTimelineService } from '@/core/FunoutTimelineService.js';
+import { GlobalEventService } from '@/core/GlobalEventService.js';
 import { ApiError } from '../../error.js';
 
 export const meta = {
@@ -71,6 +72,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private queryService: QueryService,
 		private noteReadService: NoteReadService,
 		private funoutTimelineService: FunoutTimelineService,
+		private globalEventService: GlobalEventService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
 			const untilId = ps.untilId ?? (ps.untilDate ? this.idService.gen(ps.untilDate!) : null);
@@ -85,10 +87,16 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				throw new ApiError(meta.errors.noSuchAntenna);
 			}
 
-			this.antennasRepository.update(antenna.id, {
-				isActive: true,
-				lastUsedAt: new Date(),
-			});
+			// falseだった場合はアンテナの配信先が増えたことを通知したい
+			const needPublishEvent = !antenna.isActive;
+
+			antenna.isActive = true;
+			antenna.lastUsedAt = new Date();
+			this.antennasRepository.update(antenna.id, antenna);
+
+			if (needPublishEvent) {
+				this.globalEventService.publishInternalEvent('antennaUpdated', antenna);
+			}
 
 			let noteIds = await this.funoutTimelineService.get(`antennaTimeline:${antenna.id}`, untilId, sinceId);
 			noteIds = noteIds.slice(0, ps.limit);