diff --git a/src/remote/activitypub/models/note.ts b/src/remote/activitypub/models/note.ts
index 221d502f06..ab6dd99a77 100644
--- a/src/remote/activitypub/models/note.ts
+++ b/src/remote/activitypub/models/note.ts
@@ -76,7 +76,7 @@ export async function createNote(value: any, resolver?: Resolver, silent = false
 	const { window } = new JSDOM(note.content);
 
 	// ユーザーの情報が古かったらついでに更新しておく
-	if (actor.updatedAt && Date.now() - actor.updatedAt.getTime() > 1000 * 60 * 60 * 24) {
+	if (actor.updatedAt == null || Date.now() - actor.updatedAt.getTime() > 1000 * 60 * 60 * 24) {
 		updatePerson(note.attributedTo);
 	}