diff --git a/layout/style/test/test_specified_value_serialization.html b/layout/style/test/test_specified_value_serialization.html
index b9ace61d1046..d0aca8b3c3e0 100644
--- a/layout/style/test/test_specified_value_serialization.html
+++ b/layout/style/test/test_specified_value_serialization.html
@@ -270,6 +270,10 @@
     }
   });
 
+  p.style.paintOrder = "markers";
+  is(p.style.paintOrder, "markers",
+     "specified value serialization for paint-order doesn't contain repetitive values");
+
   p.remove();
 })();