diff --git a/test/parallel/test-debug-port-cluster.js b/test/parallel/test-debug-port-cluster.js
index 05e1627265b524..2f65ab05d688df 100644
--- a/test/parallel/test-debug-port-cluster.js
+++ b/test/parallel/test-debug-port-cluster.js
@@ -1,12 +1,12 @@
 'use strict';
-var common = require('../common');
-var assert = require('assert');
-var spawn = require('child_process').spawn;
+const common = require('../common');
+const assert = require('assert');
+const spawn = require('child_process').spawn;
 
 const PORT_MIN = common.PORT + 1337;
 const PORT_MAX = PORT_MIN + 2;
 
-var args = [
+const args = [
   '--debug=' + PORT_MIN,
   common.fixturesDir + '/clustered-server/app.js'
 ];
@@ -14,14 +14,18 @@ var args = [
 const child = spawn(process.execPath, args);
 child.stderr.setEncoding('utf8');
 
+const checkMessages = common.mustCall(() => {
+  for (let port = PORT_MIN; port <= PORT_MAX; port += 1) {
+    assert(stderr.includes(`Debugger listening on port ${port}`));
+  }
+});
+
 let stderr = '';
 child.stderr.on('data', (data) => {
+  process.stderr.write(`[DATA] ${data}`);
   stderr += data;
-  if (child.killed !== true && stderr.includes('all workers are running'))
+  if (child.killed !== true && stderr.includes('all workers are running')) {
     child.kill();
-});
-
-process.on('exit', () => {
-  for (let port = PORT_MIN; port <= PORT_MAX; port += 1)
-    assert(stderr.includes(`Debugger listening on port ${port}`));
+    checkMessages();
+  }
 });