diff --git a/lib/tick.ts b/lib/tick.ts
index a4b8c2b..d158357 100644
--- a/lib/tick.ts
+++ b/lib/tick.ts
@@ -1,13 +1,9 @@
-import { Cancel, Source } from "./source";
+import { Source } from "./source";
 
 export type PhysicsTick = ["physics"];
 export type RenderTick = ["render", number];
 
 export function tick(fps: number): Source<PhysicsTick | RenderTick> {
-  function tickSource(): PhysicsTick;
-  function tickSource(
-    callback: (tick: PhysicsTick | RenderTick) => void
-  ): Cancel;
   function tickSource(callback?: (tick: PhysicsTick | RenderTick) => void) {
     if (callback) {
       let lastPhysicsTick: number = new Date().getTime();
@@ -32,5 +28,5 @@ export function tick(fps: number): Source<PhysicsTick | RenderTick> {
     }
   }
 
-  return tickSource;
+  return tickSource as Source<PhysicsTick | RenderTick>;
 }