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diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-document-opacity-image.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-document-opacity-image.html
new file mode 100644
index 0000000000..e407f68708
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+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-document-opacity-image.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html class="hide">
+<head>
+<title>Performance Paint Timing Test: Image FCP due to the documentElement's opacity</title>
+<style>
+    html {
+      will-change: opacity;
+    }
+    .hide {
+        opacity: 0;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main"></div>
+<script>
+// Load the image, add it to the DOM and make sure it's decoded.
+const load_image = () => {
+  const img = document.createElement("img");
+  img.src = "../resources/circles.png";
+  document.body.appendChild(img);
+  return img.decode();
+};
+
+const change_opacity = () => {
+  document.documentElement.className = "";
+}
+
+promise_test(async t => {
+  assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+  await load_image();
+  await assertNoFirstContentfulPaint(t);
+  change_opacity();
+  await waitForAnimationFrames(3);
+  const fcp_entries = performance.getEntriesByName('first-contentful-paint');
+  assert_equals(fcp_entries.length, 1, "Got an FCP entry");
+  const lcp_entries = await new Promise(resolve => {new PerformanceObserver((list) => resolve(list.getEntries())).observe({type: 'largest-contentful-paint', buffered: true})});
+  assert_equals(lcp_entries.length, 1, "Got an LCP entry");
+  // TODO: Rewrite this assertion after the FCP and LCP precision alignment CL is landed. Currently FCP start time has a higher precision than that of LCP. That means, even if the two are intrinsically the same, FCP.startTime will be larger as it has more fractional digits.
+  isLess = fcp_entries[0].startTime < lcp_entries[0].startTime;
+  isEqualToMicrosecond = Math.abs(fcp_entries[0].startTime - lcp_entries[0].startTime) < 0.001;
+  assert_true(isLess || isEqualToMicrosecond, "FCP should be smaller than FCP.");
+}, "Test that FCP after opacity change is not a larger value than LCP");
+</script>
+</body>
+</html>