diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3c3aa50536df..fc463c03178b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 ### Client
 
 ### Server
+- 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 (pick #14059)
 
 ## 2024.5.0-kinel.2
 
diff --git a/packages/backend/src/queue/processors/DeliverProcessorService.ts b/packages/backend/src/queue/processors/DeliverProcessorService.ts
index b73195afc3f8..d665945861e2 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();