diff --git a/test/pummel/test-hash-seed.js b/test/pummel/test-hash-seed.js
index fd59bbe5e0653c..2b7f13593a9aa4 100644
--- a/test/pummel/test-hash-seed.js
+++ b/test/pummel/test-hash-seed.js
@@ -2,19 +2,30 @@
 
 // Check that spawn child doesn't create duplicated entries
 require('../common');
+const Countdown = require('../common/countdown');
 const REPETITIONS = 2;
 const assert = require('assert');
 const fixtures = require('../common/fixtures');
-const { spawnSync } = require('child_process');
+const { spawn } = require('child_process');
 const targetScript = fixtures.path('guess-hash-seed.js');
 const seeds = [];
 
+const requiredCallback = () => {
+  console.log(`Seeds: ${seeds}`);
+  assert.strictEqual(new Set(seeds).size, seeds.length);
+  assert.strictEqual(seeds.length, REPETITIONS);
+};
+
+const countdown = new Countdown(REPETITIONS, requiredCallback);
+
 for (let i = 0; i < REPETITIONS; ++i) {
-  const seed = spawnSync(process.execPath, [targetScript], {
-    encoding: 'utf8'
-  }).stdout.trim();
-  seeds.push(seed);
-}
+  let result = '';
+  const subprocess = spawn(process.execPath, [targetScript]);
+  subprocess.stdout.setEncoding('utf8');
+  subprocess.stdout.on('data', (data) => { result += data; });
 
-console.log(`Seeds: ${seeds}`);
-assert.strictEqual(new Set(seeds).size, seeds.length);
+  subprocess.on('exit', () => {
+    seeds.push(result.trim());
+    countdown.dec();
+  });
+}