diff --git a/fenced-frame/ancestor-throttle.https.html b/fenced-frame/ancestor-throttle.https.html
index 9b6dfb0d3051e3b..56b1320135a5c4f 100644
--- a/fenced-frame/ancestor-throttle.https.html
+++ b/fenced-frame/ancestor-throttle.https.html
@@ -17,21 +17,24 @@
 
   // Generate the url for the top level fenced frame, including the information
   // needed to pass on to its nested iframe
-  const cross_origin = get_host_info().HTTPS_REMOTE_ORIGIN;
+  const origin = get_host_info().HTTPS_REMOTE_ORIGIN;
   let fenced_frame_url = generateURL(
       "resources/ancestor-throttle-inner.https.html",
-      [ancestor_key, embed_url, cross_origin_to_top_level_iframe]);
+      [ancestor_key, embed_url, cross_origin_to_top_level_iframe], true);
   if (cross_origin_to_top_level_fenced_frame)
     fenced_frame_url = getRemoteOriginURL(fenced_frame_url, true);
 
-  attachFencedFrame(fenced_frame_url);
+  const fenced_frame_config = await generateURNFromFledgeRawURL(
+      fenced_frame_url, [], true);
+
+  attachFencedFrame(fenced_frame_config);
 
   // There is no API to observe whether the document in the FencedFrame loaded
   // or not. Instead, set up a timeout. If the document loads, "loaded" will be
   // sent to the server. Otherwise "blocked" will be sent after 3 seconds.
   step_timeout(() => {
     writeValueToServer(ancestor_key, "blocked");
-  }, 3000);
+  }, 1000);
 
   // Get the result for the fenced frame's nested iframe.
   const fenced_frame_result = await nextValueFromServer(ancestor_key);
diff --git a/fenced-frame/csp-ancestors.https.sub.html b/fenced-frame/csp-ancestors.https.sub.html
new file mode 100644
index 000000000000000..da6c73b9dbecaba
--- /dev/null
+++ b/fenced-frame/csp-ancestors.https.sub.html
@@ -0,0 +1,43 @@
+<!DOCTYPE html>
+<title>Test Content-Security-Policy frame-ancestors</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/utils.js"></script>
+<script src="/common/dispatcher/dispatcher.js"></script>
+<script src="resources/utils.js"></script>
+<script src="/common/get-host-info.sub.js"></script>
+<body>
+<script>
+promise_test(async (t) => {
+  // The fenced frame loads with a frame-ancestors policy set. The only way for
+  // the fenced frame to know that it can't load is if it checks its parent's
+  // policy across the fenced frame boundary.
+  const frame = await attachFencedFrameContext({
+    headers: [[
+      'Content-Security-Policy',
+      'frame-ancestors {{hosts[alt][www1]}}:{{ports[https][0]}}'
+    ]]
+  });
+  let timeout_promise =
+      new Promise(resolve => t.step_timeout(() => resolve('timeout'), 1000));
+  let execute_promise = frame.execute(() => {});
+  const result = await Promise.race([timeout_promise, execute_promise]);
+  assert_equals(result, 'timeout', 'The fenced frame should not load');
+}, 'Fenced frames check beyond fenced boundary for CSP frame-ancestors');
+
+promise_test(async () => {
+  // The Protected Audience fenced frame loads with a frame-ancestors policy
+  // set. It should be allowed to load even though the parent's origin isn't
+  // part of the policy.
+  const frame = await attachFencedFrameContext({
+    generator_api: 'fledge',
+    headers: [[
+      'Content-Security-Policy',
+      'frame-ancestors {{hosts[alt][www1]}}:{{ports[https][0]}}'
+    ]]
+  });
+  await frame.execute(() => {});
+}, 'Protected Audience fenced frames do not check beyond fenced boundary for ' +
+   'CSP frame-ancestors');
+</script>
+</body>
