diff --git a/packages/backend/test/unit/activitypub.ts b/packages/backend/test/unit/activitypub.ts
index 31f359e6d7..bdd08059fe 100644
--- a/packages/backend/test/unit/activitypub.ts
+++ b/packages/backend/test/unit/activitypub.ts
@@ -109,6 +109,9 @@ describe('ActivityPub', () => {
 	const meta = metaInitial;
 
 	function updateMeta(newMeta: Partial<MiMeta>): void {
+		for (const key in meta) {
+			delete (meta as any)[key];
+		}
 		Object.assign(meta, newMeta);
 	}