diff --git a/service-workers/redirects/opaque-redirect.window.js b/service-workers/redirects/opaque-redirect.window.js
new file mode 100644
index 00000000000000..9ae0ba583c0d98
--- /dev/null
+++ b/service-workers/redirects/opaque-redirect.window.js
@@ -0,0 +1,13 @@
+// META: script=../service-worker/resources/test-helpers.sub.js
+
+promise_test(async t => {
+  const reg = await service_worker_unregister_and_register(t, "resources/opaque-redirect-serviceworker.js", "resources/");
+  t.add_cleanup(async () => await reg.unregister());
+  await wait_for_state(t, reg.installing, 'activated');
+  const frame = await with_iframe("resources/opaque-redirect.py");
+  assert_equals(frame.contentDocument.body.textContent, "stage 1 completed\n");
+  frame.remove();
+  const frame2 = await with_iframe("resources/x/");
+  assert_equals(frame2.contentDocument.body.textContent, "YAY!\n");
+  frame2.remove();
+}, "Passing an (opaque) redirect with a relative URL in its Location header to a second navigation with a different base URL");
diff --git a/service-workers/redirects/resources/opaque-redirect-result.txt b/service-workers/redirects/resources/opaque-redirect-result.txt
new file mode 100644
index 00000000000000..07103062557c8a
--- /dev/null
+++ b/service-workers/redirects/resources/opaque-redirect-result.txt
@@ -0,0 +1 @@
+YAY!
diff --git a/service-workers/redirects/resources/opaque-redirect-serviceworker.js b/service-workers/redirects/resources/opaque-redirect-serviceworker.js
new file mode 100644
index 00000000000000..4b336074e5f2ac
--- /dev/null
+++ b/service-workers/redirects/resources/opaque-redirect-serviceworker.js
@@ -0,0 +1,11 @@
+let evilGlobalState = null;
+onfetch = e => {
+  if(e.request.url.endsWith("resources/opaque-redirect.py")) {
+    e.respondWith(new Promise(async resolve => {
+      evilGlobalState = await fetch(e.request);
+      resolve(new Response("stage 1 completed\n"));
+    }));
+  } else if(e.request.url.endsWith("resources/x/")) {
+    e.respondWith(evilGlobalState);
+  }
+}
diff --git a/service-workers/redirects/resources/opaque-redirect.py b/service-workers/redirects/resources/opaque-redirect.py
new file mode 100644
index 00000000000000..c490bfa5bd6db6
--- /dev/null
+++ b/service-workers/redirects/resources/opaque-redirect.py
@@ -0,0 +1,3 @@
+def main(request, response):
+    response.status = 302
+    response.headers.set("Location", "opaque-redirect-result.txt")
diff --git a/service-workers/redirects/resources/x/opaque-redirect-result.txt b/service-workers/redirects/resources/x/opaque-redirect-result.txt
new file mode 100644
index 00000000000000..2d80cb9469bc32
--- /dev/null
+++ b/service-workers/redirects/resources/x/opaque-redirect-result.txt
@@ -0,0 +1 @@
+NOOO :-(