diff --git a/layout/reftests/forms/legend/1339287-ref.html b/layout/reftests/forms/legend/1339287-ref.html
new file mode 100644
index 000000000000..8dea047bbd14
--- /dev/null
+++ b/layout/reftests/forms/legend/1339287-ref.html
@@ -0,0 +1,46 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Testcase for bug 1339287</title>
+  <style type="text/css">
+
+html,body {
+  color:black; background-color:white; font:16px/1 monospace; padding:0; margin:0;
+}
+
+fieldset { border:1px solid black; }  /* solid border is less likely to cause AA issues */
+
+  </style>
+</head>
+<body>
+
+  <fieldset>
+    <legend style="display:inline-flex">
+      Headline Instructions
+    </legend>
+  </fieldset>
+
+  <fieldset>
+    <legend style="display:inline-grid">
+      Headline Instructions
+    </legend>
+  </fieldset>
+
+  <fieldset>
+    <legend style="display:flex">
+      Headline Instructions
+    </legend>
+  </fieldset>
+
+  <fieldset>
+    <legend style="display:grid">
+      Headline Instructions
+    </legend>
+  </fieldset>
+
+</body>
+</html>
diff --git a/layout/reftests/forms/legend/1339287.html b/layout/reftests/forms/legend/1339287.html
new file mode 100644
index 000000000000..482663f79fb8
--- /dev/null
+++ b/layout/reftests/forms/legend/1339287.html
@@ -0,0 +1,58 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <meta charset="utf-8">
+  <title>Testcase for bug 1339287</title>
+  <style type="text/css">
+
+html,body {
+  color:black; background-color:white; font:16px/1 monospace; padding:0; margin:0;
+}
+
+fieldset { border:1px solid black; }  /* solid border is less likely to cause AA issues */
+
+  </style>
+</head>
+<body>
+
+  <fieldset>
+    <legend style="display:inline-flex">
+      Headline 
+      <span>
+        Instructions
+       </span>
+    </legend>
+  </fieldset>
+
+  <fieldset>
+    <legend style="display:inline-grid">
+      Headline 
+      <span>
+        Instructions
+       </span>
+    </legend>
+  </fieldset>
+
+  <fieldset>
+    <legend style="display:flex">
+      Headline 
+      <span>
+        Instructions
+       </span>
+    </legend>
+  </fieldset>
+
+  <fieldset>
+    <legend style="display:grid">
+      Headline 
+      <span>
+        Instructions
+       </span>
+    </legend>
+  </fieldset>
+
+</body>
+</html>
diff --git a/layout/reftests/forms/legend/reftest.list b/layout/reftests/forms/legend/reftest.list
index 879835a59bea..279cc9aea8a7 100644
--- a/layout/reftests/forms/legend/reftest.list
+++ b/layout/reftests/forms/legend/reftest.list
@@ -1,3 +1,4 @@
 == legend.html legend-ref.html
 fuzzy-if(skiaContent,1,7) pref(dom.webcomponents.enabled,true) == shadow-dom.html shadow-dom-ref.html
 == 1273433.html 1273433-ref.html
+== 1339287.html 1339287-ref.html
