--- a/dom/animation/test/chrome/test_restyles.html
+++ b/dom/animation/test/chrome/test_restyles.html
@@ -757,19 +757,19 @@ waitForAllPaints(function() {
     is(markers.length, 0,
        'Animation on orphaned element should not cause restyles');
 
     document.body.appendChild(div);
 
     markers = await observeStyling(1);
     // Bug 1388557: We should call RequestRestyle(Layer) when an element which
     // has running script animations is attached to document.
-    is(markers.length, 0,
-       'We observe no restyle in the first frame right after re-attaching ' +
-       'to the document');
+    todo_is(markers.length, 1,
+            'Bug 1388557 We should observe one restyle in the first frame ' +
+            'right after re-attaching to the document');
     markers = await observeStyling(5);
     is(markers.length, 5,
        'Animation on re-attached to the document begins to update style');
 
     await ensureElementRemoval(div);
   });
 
   add_task_if_omta_enabled(