diff --git a/packages/backend/src/core/activitypub/ApRendererService.ts b/packages/backend/src/core/activitypub/ApRendererService.ts
index 8f436f343d..4dfedad2e6 100644
--- a/packages/backend/src/core/activitypub/ApRendererService.ts
+++ b/packages/backend/src/core/activitypub/ApRendererService.ts
@@ -595,10 +595,10 @@ export class ApRendererService {
 	}
 
 	@bindThis
-	public renderNoteUpdate(object: IPost, note: MiNote, user: { id: MiUser['id'] }): IUpdate {
+	public renderNoteUpdate(object: IPost, user: { id: MiUser['id'] }): IUpdate {
 		const activity: IUpdate = {
 			id: `${this.config.url}/users/${user.id}#updates/${new Date().getTime()}`,
-			actor: this.userEntityService.genLocalUserUri(note.userId),
+			actor: this.userEntityService.genLocalUserUri(user.id),
 			type: 'Update',
 			published: new Date().toISOString(),
 			object,
diff --git a/packages/backend/test/unit/activitypub.ts b/packages/backend/test/unit/activitypub.ts
index 2ebf6c056a..d3d4ab880a 100644
--- a/packages/backend/test/unit/activitypub.ts
+++ b/packages/backend/test/unit/activitypub.ts
@@ -399,15 +399,15 @@ describe('ActivityPub', () => {
 				content: 'あ',
 			};
 
+			resolver.register(actor.id, actor);
+			resolver.register(post.id, post);
+
 			const note = {
 				...(await noteService.createNote(post.id, resolver, true))!,
 				updatedAt: new Date(),
 			};
 
-			resolver.register(actor.id, actor);
-			resolver.register(post.id, post);
-
-			rendererService.renderNoteUpdate(await rendererService.renderNote(note, false, true), note, actor);
+			rendererService.renderNoteUpdate(await rendererService.renderNote(note, false, true), actor);
 		});
 	});