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diff --git a/testing/web-platform/tests/css/css-writing-modes/wm-propagation-body-scroll-offset-vertical-rl.html b/testing/web-platform/tests/css/css-writing-modes/wm-propagation-body-scroll-offset-vertical-rl.html
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+++ b/testing/web-platform/tests/css/css-writing-modes/wm-propagation-body-scroll-offset-vertical-rl.html
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+<!DOCTYPE html>
+<meta charset="UTF-8">
+<title>CSS Writing Modes Test: body vertical-rl propagated to viewport - scroll direction</title>
+<link rel="author" title="Rune Lillesveen" href="mailto:rune@opera.com">
+<link rel="help" href="https://www.w3.org/TR/css-writing-modes-3/#principal-flow">
+<meta name="assert" content="Test that propagating writing-mode from body to viewport affects scroll direction">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<style>
+  html { writing-mode: vertical-lr; }
+  body { writing-mode: vertical-rl; width: 10000px; }
+
+  .result-wm, .result-wm > body {
+    writing-mode: horizontal-tb;
+    width: auto;
+  }
+</style>
+<body>
+<script>
+  test(function() {
+    assert_equals(document.scrollingElement.scrollLeft, 0, "scrollLeft should be 0.");
+  }, "Check initial scroll position of viewport.");
+
+  test(function() {
+    document.scrollingElement.scrollLeft = -1000;
+    assert_equals(document.scrollingElement.scrollLeft, -1000, "scrollLeft should be -1000.");
+  }, "Scroll to scrollLeft = -1000 should be possible.");
+
+  test(function() {
+    document.scrollingElement.scrollLeft = 1000;
+    assert_equals(document.scrollingElement.scrollLeft, 0, "scrollLeft should be 0.");
+  }, "Scroll to scrollLeft = 1000 should not be possible.");
+
+  // Reset back to horizontal-tb to make the result readable on-screen.
+  document.scrollingElement.className = "result-wm";
+</script>