diff --git a/testing/web-platform/tests/fullscreen/rendering/backdrop-iframe-ref.html b/testing/web-platform/tests/fullscreen/rendering/backdrop-green-ref.html
similarity index 100%
rename from testing/web-platform/tests/fullscreen/rendering/backdrop-iframe-ref.html
rename to testing/web-platform/tests/fullscreen/rendering/backdrop-green-ref.html
diff --git a/testing/web-platform/tests/fullscreen/rendering/backdrop-iframe.html b/testing/web-platform/tests/fullscreen/rendering/backdrop-iframe.html
index 710d1b48f182d..dbdf9c841a468 100644
--- a/testing/web-platform/tests/fullscreen/rendering/backdrop-iframe.html
+++ b/testing/web-platform/tests/fullscreen/rendering/backdrop-iframe.html
@@ -1,7 +1,7 @@
 <!DOCTYPE html>
 <html class=reftest-wait>
 <title>::backdrop for a fullscreen iframe element</title>
-<link rel=match href="backdrop-iframe-ref.html">
+<link rel=match href="backdrop-green-ref.html">
 <link rel=help href="https://github.com/w3c/csswg-drafts/issues/6939">
 <script src="/resources/testdriver.js"></script>
 <script src="/resources/testdriver-vendor.js"></script>
diff --git a/testing/web-platform/tests/fullscreen/rendering/backdrop-inherit.html b/testing/web-platform/tests/fullscreen/rendering/backdrop-inherit.html
new file mode 100644
index 0000000000000..3a38dc4c81526
--- /dev/null
+++ b/testing/web-platform/tests/fullscreen/rendering/backdrop-inherit.html
@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<title>::backdrop inherits style from the fullscreen element</title>
+<link rel=match href="backdrop-green-ref.html">
+<link rel=help href="https://github.com/whatwg/fullscreen/issues/124">
+<script src="/resources/testdriver.js"></script>
+<script src="/resources/testdriver-vendor.js"></script>
+<style>
+body {
+  --bg: red;
+}
+div {
+  --bg: green;
+}
+div::backdrop {
+  background: var(--bg);
+}
+</style>
+<div></div>
+<script>
+document.addEventListener('fullscreenchange', () => {
+  document.documentElement.classList.remove('reftest-wait');
+});
+test_driver.bless('fullscreen', () => {
+  document.querySelector('div').requestFullscreen();
+});
+</script>
