diff --git a/packages/backend/src/misc/i18n.ts b/packages/backend/src/misc/i18n.ts
index 4fa398763..9a18cf449 100644
--- a/packages/backend/src/misc/i18n.ts
+++ b/packages/backend/src/misc/i18n.ts
@@ -13,7 +13,7 @@ export class I18n<T extends Record<string, any>> {
 	// なるべくこのメソッド使うよりもlocale直接参照の方がvueのキャッシュ効いてパフォーマンスが良いかも
 	public t(key: string, args?: Record<string, any>): string {
 		try {
-			let str = key.split('.').reduce((o, i) => o[i], this.locale) as string;
+			let str = key.split('.').reduce((o, i) => o[i] as Record<string, any> | string, this.locale) as string;
 
 			if (args) {
 				for (const [k, v] of Object.entries(args)) {