diff --git a/mozilla/layout/reftests/bugs/240470-1-ref.html b/mozilla/layout/reftests/bugs/240470-1-ref.html
new file mode 100644
index 00000000000..e56d951133d
--- /dev/null
+++ b/mozilla/layout/reftests/bugs/240470-1-ref.html
@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<body>
+<html>
+<select id="test" size="8">
+</select>
+<script>
+  var optgroup = document.createElement("optgroup");
+  optgroup.setAttribute('label', 'An optgroup');
+  var option = document.createElement("option");
+  var optionText = document.createTextNode("An option");
+  option.appendChild(optionText);
+  var select = document.getElementById("test");
+
+  optgroup.appendChild(option);
+  select.appendChild(optgroup);
+</script>
+</body>
+</html>
diff --git a/mozilla/layout/reftests/bugs/240470-1.html b/mozilla/layout/reftests/bugs/240470-1.html
new file mode 100644
index 00000000000..307a07376b8
--- /dev/null
+++ b/mozilla/layout/reftests/bugs/240470-1.html
@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<body>
+<html>
+<select id="test" size="8">
+</select>
+<script>
+  var optgroup = document.createElement("optgroup");
+  optgroup.setAttribute('label', 'An optgroup');
+  var option = document.createElement("option");
+  var optionText = document.createTextNode("An option");
+  option.appendChild(optionText);
+  var select = document.getElementById("test");
+
+  select.appendChild(optgroup);
+  optgroup.appendChild(option);
+</script>
+</body>
+</html>
diff --git a/mozilla/layout/reftests/bugs/reftest.list b/mozilla/layout/reftests/bugs/reftest.list
index 547178c6413..8a58d402126 100644
--- a/mozilla/layout/reftests/bugs/reftest.list
+++ b/mozilla/layout/reftests/bugs/reftest.list
@@ -95,6 +95,7 @@ fails-if(MOZ_WIDGET_TOOLKIT=="cocoa") == 28811-2a.html 28811-2-ref.html # bug 38
 == 234964-2.html 234964-2-ref.html
 == 235593-1.html 235593-1-ref.html
 == 236539-1.html 236539-1-ref.html
+== 240470-1.html 240470-1-ref.html
 == 243266-1.html 243266-1-ref.html
 == 243302-1.html 243302-1-ref.html
 == 244932-1.html 244932-1-ref.html
