diff --git a/src/components/Player.tsx b/src/components/Player.tsx
index 6acc7e2..d2c3d3c 100644
--- a/src/components/Player.tsx
+++ b/src/components/Player.tsx
@@ -90,7 +90,7 @@ export function Player(props: PlayerProps) {
     const masterChannelController = props.audioSystem.getMasterChannelController();
     const fxChannelController = props.audioSystem.getFxChannelController();
 
-    const setProjectTime = (t) => props.audioSystem.update({ position: t});
+    const setProjectTime = (t: ProjectTimeSeconds) => props.audioSystem.update({ position: t});
 
     return (
         <div className="player">
diff --git a/src/zoom/formatProjectTime.ts b/src/zoom/formatProjectTime.ts
index d7dfd83..16a86db 100644
--- a/src/zoom/formatProjectTime.ts
+++ b/src/zoom/formatProjectTime.ts
@@ -1,6 +1,6 @@
 import { ProjectTimeSeconds } from './zoom_l12'
 
-function padWithZero(n) {
+function padWithZero(n: number): string {
     if (n < 10) {
         return `0${n}`;
     } else {