diff --git a/index.d.ts b/index.d.ts
index c471c71..144ba23 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,3 +1,3 @@
-declare function isObject(val: any): boolean;
+declare function isObject(val: any): val is { [key: string]: unknown };
 
 export default isObject;