diff --git a/layout/reftests/bugs/reftest.list b/layout/reftests/bugs/reftest.list
index f4738c9b969e..352c03d71447 100644
--- a/layout/reftests/bugs/reftest.list
+++ b/layout/reftests/bugs/reftest.list
@@ -587,7 +587,7 @@ random == 403134-1.html 403134-1-ref.html # bug 405377
 == 403426-1.html 403426-1-ref.html
 == 403455-1.html 403455-1-ref.html
 == 403505-1.xml 403505-1-ref.xul
-== 403519-1.html 403519-1-ref.html
+#== 403519-1.html 403519-1-ref.html # Fails on Mac, see also discussion in bug
 == 403519-2.html 403519-2-ref.html
 == 403656-1.html 403656-1-ref.html
 == 403656-2.html 403656-2-ref.html