diff --git a/packages/backend/test/utils.ts b/packages/backend/test/utils.ts
index 90a00e2096..0b5bf38cc2 100644
--- a/packages/backend/test/utils.ts
+++ b/packages/backend/test/utils.ts
@@ -696,7 +696,7 @@ export async function captureWebhook<T = SystemWebhookPayload>(postAction: () =>
 // the packed user inside each note returned by `users/notes` has the
 // latest `notesCount`, not the count at the time the note was
 // created, so we override it
-export function withNotesCount(notes, count) {
+export function withNotesCount(notes: misskey.entities.Note[], count: number) {
 	return notes.map( note => {
 		return {
 			...note,