--- a/dom/animation/test/chrome/test_animation_observers.html
+++ b/dom/animation/test/chrome/test_animation_observers.html
@@ -1535,22 +1535,23 @@ addAsyncAnimTest("tree_ordering", { obse
     yield await_frame();
     assert_records([{ added: [], changed: [anim], removed: [] }],
                    "records after duration is changed");
 
     anim.effect.timing.duration = 100 * MS_PER_SEC;
     yield await_frame();
     assert_records([], "records after assigning same value");
 
-    anim.currentTime = 500 * MS_PER_SEC;
+    anim.currentTime = anim.effect.timing.duration * 2;
+    anim.finish();
     yield await_frame();
     assert_records([{ added: [], changed: [], removed: [anim] }],
                    "records after animation end");
 
-    anim.effect.timing.duration = 1000 * MS_PER_SEC;
+    anim.effect.timing.duration = anim.effect.timing.duration * 3;
     yield await_frame();
     assert_records([{ added: [anim], changed: [], removed: [] }],
                    "records after animation restarted");
 
     anim.effect.timing.duration = "auto";
     yield await_frame();
     assert_records([{ added: [], changed: [], removed: [anim] }],
                    "records after duration set \"auto\"");