diff --git a/addon/-private/decorator.ts b/addon/-private/decorator.ts
index 1509645..2b3f7f6 100644
--- a/addon/-private/decorator.ts
+++ b/addon/-private/decorator.ts
@@ -37,7 +37,7 @@ export default function tracked<T extends object>(
 export default function tracked(
   obj: object,
   key: string | symbol,
-  desc: PropertyDescriptor
+  desc?: PropertyDescriptor
 ): void;
 
 export default function tracked(