diff --git a/types/i18next/index.d.ts b/types/i18next/index.d.ts
index 0eb8d64859..ee06d8d18c 100644
--- a/types/i18next/index.d.ts
+++ b/types/i18next/index.d.ts
@@ -108,7 +108,7 @@ declare namespace i18n {
 
         t(key: string, options?: TranslationOptions): string | any | Array<any>;
 
-        exists(key, options?: TranslationOptions): boolean;
+        exists(key: string, options?: TranslationOptions): boolean;
 
         setDefaultNamespace(ns: string): void;