diff --git a/packages/common-ts/src/eventual/__tests__/eventual.ts b/packages/common-ts/src/eventual/__tests__/eventual.ts
index 21e4289..80dc63d 100644
--- a/packages/common-ts/src/eventual/__tests__/eventual.ts
+++ b/packages/common-ts/src/eventual/__tests__/eventual.ts
@@ -286,7 +286,7 @@ describe('Eventual', () => {
   })
 
   test('Join (timer)', async () => {
-    const ticker = timer(100)
+    const [intervalID, ticker] = timer(100)
     const ticks = ticker.reduce(n => ++n, 0)
     const ticksViaJoin = join({ ticker }).reduce(n => ++n, 0)
 
@@ -296,6 +296,7 @@ describe('Eventual', () => {
     // we're happy
     await expect(ticks.value()).resolves.toBeGreaterThan(5)
     await expect(ticksViaJoin.value()).resolves.toBeGreaterThan(5)
+    clearInterval(intervalID)
   })
 
   test('Values (async generator)', async () => {
diff --git a/packages/common-ts/src/eventual/eventual.ts b/packages/common-ts/src/eventual/eventual.ts
index b69044d..ae268f2 100644
--- a/packages/common-ts/src/eventual/eventual.ts
+++ b/packages/common-ts/src/eventual/eventual.ts
@@ -286,10 +286,10 @@ export function throttle<T>(source: Eventual<T>, interval: number): Eventual<T>
   return output
 }
 
-export function timer(milliseconds: number): Eventual<number> {
+export function timer(milliseconds: number): [NodeJS.Timer, Eventual<number>] {
   const time = mutable(Date.now())
-  setInterval(() => time.push(Date.now()), milliseconds)
-  return time
+  const intervalID = setInterval(() => time.push(Date.now()), milliseconds)
+  return [intervalID, time]
 }
 
 export function reduce<T, U>(