diff --git a/CHANGELOG.md b/CHANGELOG.md
index f93811c606..e2528594c3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,7 +8,7 @@
 
 ### Server
 - チャート生成時にinstance.suspentionStateに置き換えられたinstance.isSuspendedが参照されてしまう問題を修正
-
+- Fix: notRespondingSinceが実装される前に不通になったインスタンスが自動的に配信停止にならない (#14059)
 
 ## 2024.5.0
 
diff --git a/packages/backend/src/core/FederatedInstanceService.ts b/packages/backend/src/core/FederatedInstanceService.ts
index 66db2067d9..e73e1d3a9d 100644
--- a/packages/backend/src/core/FederatedInstanceService.ts
+++ b/packages/backend/src/core/FederatedInstanceService.ts
@@ -40,6 +40,7 @@ export class FederatedInstanceService implements OnApplicationShutdown {
 					firstRetrievedAt: new Date(parsed.firstRetrievedAt),
 					latestRequestReceivedAt: parsed.latestRequestReceivedAt ? new Date(parsed.latestRequestReceivedAt) : null,
 					infoUpdatedAt: parsed.infoUpdatedAt ? new Date(parsed.infoUpdatedAt) : null,
+					notRespondingSince: parsed.notRespondingSince ? new Date(parsed.notRespondingSince) : null,
 				};
 			},
 		});
diff --git a/packages/backend/src/queue/processors/DeliverProcessorService.ts b/packages/backend/src/queue/processors/DeliverProcessorService.ts
index b73195afc3..d665945861 100644
--- a/packages/backend/src/queue/processors/DeliverProcessorService.ts
+++ b/packages/backend/src/queue/processors/DeliverProcessorService.ts
@@ -109,6 +109,12 @@ export class DeliverProcessorService {
 							suspensionState: 'autoSuspendedForNotResponding',
 						});
 					}
+				} else {
+					// isNotRespondingがtrueでnotRespondingSinceがnullの場合はnotRespondingSinceをセット
+					// notRespondingSinceは新たな機能なので、それ以前のデータにはnotRespondingSinceがない場合がある
+					this.federatedInstanceService.update(i.id, {
+						notRespondingSince: new Date(),
+					});
 				}
 
 				this.apRequestChart.deliverFail();