diff --git a/packages/client/src/init.ts b/packages/client/src/init.ts
index 89692d5fb..508d3262b 100644
--- a/packages/client/src/init.ts
+++ b/packages/client/src/init.ts
@@ -128,7 +128,7 @@ import { getAccountFromId } from '@/scripts/get-account-from-id';
 		}
 
 		// 連携ログインの場合用にCookieを参照する
-		const i = (document.cookie.match(/igi=(\w+)/) || [null, null])[1];
+		const i = (document.cookie.match(/igi=(\w+)/) ?? [null, null])[1];
 
 		if (i != null && i !== 'null') {
 			if (_DEV_) {