diff --git a/types/plugin/updateLocale.d.ts b/types/plugin/updateLocale.d.ts
index 44bce470d..ef1c01df9 100644
--- a/types/plugin/updateLocale.d.ts
+++ b/types/plugin/updateLocale.d.ts
@@ -4,5 +4,5 @@ declare const plugin: PluginFunc
 export = plugin
 
 declare module 'dayjs' {
-  export function updateLocale(localeName: String, customConfig: Object): any
+  export function updateLocale(localeName: string, customConfig: Record<string, unknown>): Record<string, unknown>
 }