diff --git a/gluon.d.ts b/gluon.d.ts
index 18d5258..95be650 100644
--- a/gluon.d.ts
+++ b/gluon.d.ts
@@ -80,7 +80,7 @@ type IdleApi = {
 
     /** Set options for automatic behavior. */
     options?: IdleAutoOptions
-  )
+  ): void
 };
 
 type Window = {