diff --git a/index.d.ts b/index.d.ts
index 74bf577..e0b1302 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -5,11 +5,8 @@
  * @param signal 'SIGTERM' by default
  * @param callback
  */
-declare function treeKill(
-    pid: number,
-    signal?: string | number,
-    callback?: (error?: Error) => void,
-): void;
+declare function treeKill(pid: number, callback?: (error?: Error) => void): void;
+declare function treeKill(pid: number, signal?: string | number, callback?: (error?: Error) => void): void;
 
 declare namespace treeKill {}