diff --git a/workers/modules/shared-worker-parse-error-failure.html b/workers/modules/shared-worker-parse-error-failure.html
index f6f13405035edaf..d3d86b3f8fca9c5 100644
--- a/workers/modules/shared-worker-parse-error-failure.html
+++ b/workers/modules/shared-worker-parse-error-failure.html
@@ -27,21 +27,31 @@
   );
 });
 
+const checkArguments = (args) => {
+  assert_equals(args.a.constructor, Event);
+  assert_true('message' in args.a, 'Event.message');
+  assert_equals(typeof args.a.message, 'string', 'Event.message');
+  assert_equals(args.a.filename, location.href + '/resources/syntax-error.js');
+  assert_equals(args.a.lineno, 1, 'Event.lineno');
+  assert_equals(args.b, undefined, 'unexpected second argument to onerror');
+  assert_equals(args.c, undefined, 'unexpected third argument to onerror');
+};
+
 promise_test(async () => {
   const scriptURL = 'resources/syntax-error.js';
   const worker = new SharedWorker(scriptURL, { type: 'module' });
-  const type = await new Promise(resolve =>
-      worker.onerror = error => resolve(error.type));
-  assert_equals(type, 'error');
+  const args = await new Promise(resolve =>
+      worker.onerror = (a, b, c) => resolve({a, b, c}));
+  checkArguments(args);
 }, 'Module shared worker construction for script with syntax error should ' +
    'dispatch an event named error.');
 
 promise_test(async () => {
   const scriptURL = 'resources/static-import-syntax-error.js';
   const worker = new SharedWorker(scriptURL, { type: 'module' });
-  const type = await new Promise(resolve =>
-      worker.onerror = error => resolve(error.type));
-  assert_equals(type, 'error');
+  const args = await new Promise(resolve =>
+      worker.onerror = (a, b, c) => resolve({a, b, c}));
+  checkArguments(args);
 }, 'Static import on module shared worker for script with syntax error ' +
    'should dispatch an event named error.');
 
diff --git a/workers/shared-worker-parse-error-failure.html b/workers/shared-worker-parse-error-failure.html
index dc4ad1d7700a04c..5f98e59d8fe8aea 100644
--- a/workers/shared-worker-parse-error-failure.html
+++ b/workers/shared-worker-parse-error-failure.html
@@ -4,21 +4,31 @@
 <script src="/resources/testharnessreport.js"></script>
 <script>
 
+const checkArguments = (args) => {
+  assert_equals(args.a.constructor, Event);
+  assert_true('message' in args.a, 'Event.message');
+  assert_equals(typeof args.a.message, 'string', 'Event.message');
+  assert_equals(args.a.filename, location.href + '/resources/syntax-error.js');
+  assert_equals(args.a.lineno, 1, 'Event.lineno');
+  assert_equals(args.b, undefined, 'unexpected second argument to onerror');
+  assert_equals(args.c, undefined, 'unexpected third argument to onerror');
+};
+
 promise_test(async () => {
   const scriptURL = 'modules/resources/syntax-error.js';
   const worker = new SharedWorker(scriptURL, { type: 'classic' });
-  const type = await new Promise(resolve =>
-      worker.onerror = error => resolve(error.type));
-  assert_equals(type, 'error');
+  const args = await new Promise(resolve =>
+      worker.onerror = (a, b, c) => resolve({a, b, c}));
+  checkArguments(args);
 }, 'Classic shared worker construction for script with syntax error should ' +
    'dispatch an event named error.');
 
 promise_test(async () => {
   const scriptURL = 'modules/resources/static-import-worker.js';
   const worker = new SharedWorker(scriptURL, { type: 'classic' });
-  const type = await new Promise(resolve =>
-      worker.onerror = error => resolve(error.type));
-  assert_equals(type, 'error');
+  const args = await new Promise(resolve =>
+      worker.onerror = (a, b, c) => resolve({a, b, c}));
+  checkArguments(args);
 }, 'Static import on classic shared worker should dispatch an event named ' +
    'error.');