diff --git a/css/css-fonts/font-size-monospace-adjust-ref.html b/css/css-fonts/font-size-monospace-adjust-ref.html
new file mode 100644
index 00000000000000..098fca5ea76ff3
--- /dev/null
+++ b/css/css-fonts/font-size-monospace-adjust-ref.html
@@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<style>
+  textarea { font-size: 3em; }
+</style>
+<textarea>Textarea</textarea>
diff --git a/css/css-fonts/font-size-monospace-adjust.html b/css/css-fonts/font-size-monospace-adjust.html
new file mode 100644
index 00000000000000..f1a0b7294d3502
--- /dev/null
+++ b/css/css-fonts/font-size-monospace-adjust.html
@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<link rel="help" href="https://crbug.com/1086082">
+<link rel="match" href="font-size-monospace-adjust-ref.html">
+<style>
+  textarea {
+    font-size: 3em;
+    transition: margin-bottom 1e10s steps(2, start);
+    margin-bottom: 10px;
+  }
+
+  .margin {
+    margin-bottom: 20px;
+  }
+</style>
+<textarea id=textarea>Textarea</textarea>
+<script>
+  document.documentElement.offsetTop;
+  textarea.classList.toggle('margin');
+</script>
