diff --git a/src/simulator/src/sequential.js b/src/simulator/src/sequential.ts
similarity index 70%
rename from src/simulator/src/sequential.js
rename to src/simulator/src/sequential.ts
index 46dcd6932..25ad21248 100644
--- a/src/simulator/src/sequential.js
+++ b/src/simulator/src/sequential.ts
@@ -5,6 +5,7 @@ import { simulationArea } from './simulationArea'
  * a global function as a helper for simulationArea.changeClockEnable
  * @category sequential
  */
-export function changeClockEnable(val) {
-    simulationArea.clockEnabled = val
+export function changeClockEnable(val: boolean): void {
+  simulationArea.clockEnabled = val
 }
+