diff --git a/layout/reftests/editor/reftest.list b/layout/reftests/editor/reftest.list
index 6e36355c2160..baf4c4cd200f 100644
--- a/layout/reftests/editor/reftest.list
+++ b/layout/reftests/editor/reftest.list
@@ -13,7 +13,7 @@ include xul/reftest.list
 == passwd-1.html passwd-ref.html
 != passwd-2.html passwd-ref.html
 == passwd-3.html passwd-ref.html
-== passwd-4.html passwd-ref.html
+asserts(1) == passwd-4.html passwd-ref.html # bug 596901
 == emptypasswd-1.html emptypasswd-ref.html
 == emptypasswd-2.html emptypasswd-ref.html
 == caret_on_positioned.html caret_on_positioned-ref.html