diff --git a/src/remote/activitypub/act/undo/index.ts b/src/remote/activitypub/act/undo/index.ts
index 38d5bfe211..11c7ec0c83 100644
--- a/src/remote/activitypub/act/undo/index.ts
+++ b/src/remote/activitypub/act/undo/index.ts
@@ -2,7 +2,7 @@ import act from '../../act';
 import unfollow from './unfollow';
 import Resolver from '../../resolver';
 
-export default async (resolver: Resolver, actor, activity) => {
+export default async (resolver: Resolver, actor, activity): Promise<void> => {
 	if ('actor' in activity && actor.account.uri !== activity.actor) {
 		throw new Error();
 	}
@@ -21,6 +21,4 @@ export default async (resolver: Resolver, actor, activity) => {
 			await unfollow(result.object);
 		}
 	}));
-
-	return null;
 };