diff --git a/test/common/wpt.js b/test/common/wpt.js
index 9b359877b29edd..cc7c5320fa972e 100644
--- a/test/common/wpt.js
+++ b/test/common/wpt.js
@@ -468,9 +468,10 @@ const limit = (concurrency) => {
 };
 
 class WPTRunner {
-  constructor(path) {
+  constructor(path, { concurrency = os.availableParallelism() - 1 || 1 } = {}) {
     this.path = path;
     this.resource = new ResourceLoader(path);
+    this.concurrency = concurrency;
 
     this.flags = [];
     this.globalThisInitScripts = [];
@@ -595,7 +596,7 @@ class WPTRunner {
   async runJsTests() {
     const queue = this.buildQueue();
 
-    const run = limit(os.availableParallelism());
+    const run = limit(this.concurrency);
 
     for (const spec of queue) {
       const content = spec.getContent();
diff --git a/test/wpt/test-timers.js b/test/wpt/test-timers.js
index 86b1cf35b80629..efc2ee6e1ea6e8 100644
--- a/test/wpt/test-timers.js
+++ b/test/wpt/test-timers.js
@@ -2,6 +2,6 @@
 
 const { WPTRunner } = require('../common/wpt');
 
-const runner = new WPTRunner('html/webappapis/timers');
+const runner = new WPTRunner('html/webappapis/timers', { concurrency: 1 });
 
 runner.runJsTests();
diff --git a/test/wpt/testcfg.py b/test/wpt/testcfg.py
index db235699ddfe57..3c356cf474d83c 100644
--- a/test/wpt/testcfg.py
+++ b/test/wpt/testcfg.py
@@ -3,4 +3,4 @@
 import testpy
 
 def GetConfiguration(context, root):
-  return testpy.ParallelTestConfiguration(context, root, 'wpt')
+  return testpy.SimpleTestConfiguration(context, root, 'wpt')