diff --git a/src/entry/worker.ts b/src/entry/worker.ts
index 40eb3ae..78a3527 100644
--- a/src/entry/worker.ts
+++ b/src/entry/worker.ts
@@ -49,6 +49,8 @@ parentPort!.on('message', (message: StartupMessage) => {
     const readyMessage: ReadyMessage = { ready: true }
     parentPort!.postMessage(readyMessage)
 
+    port.start()
+
     port.on('message', onMessage.bind(null, port, sharedBuffer))
     atomicsWaitLoop(port, sharedBuffer)
   })().catch(throwInNextTick)
diff --git a/src/index.ts b/src/index.ts
index 01c71d6..eef0ecc 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -791,6 +791,8 @@ class ThreadPool {
 
     worker.on('message', (message: ReadyMessage) => {
       if (message.ready === true) {
+        port1.start()
+
         if (workerInfo.currentUsage() === 0) {
           workerInfo.unref()
         }
diff --git a/src/runtime/process-worker.ts b/src/runtime/process-worker.ts
index ca96aa4..50a2316 100644
--- a/src/runtime/process-worker.ts
+++ b/src/runtime/process-worker.ts
@@ -92,6 +92,7 @@ export default class ProcessWorker implements TinypoolWorker {
     transferListItem?.forEach((item) => {
       if (item instanceof MessagePort) {
         this.port = item
+        this.port.start()
       }
     })
 
@@ -149,7 +150,7 @@ export default class ProcessWorker implements TinypoolWorker {
 
     // The forked child_process adds event listener on `process.on('message)`.
     // This requires manual unreffing of its channel.
-    this.process.channel?.unref()
+    this.process.channel?.unref?.()
 
     if (hasUnref(this.process.stdout)) {
       this.process.stdout.unref()