diff --git a/dom/animation/Animation.cpp b/dom/animation/Animation.cpp
index 82cafd19dcf0..51deed950336 100644
--- a/dom/animation/Animation.cpp
+++ b/dom/animation/Animation.cpp
@@ -650,7 +650,7 @@ void Animation::Tick() {
     FinishPendingAt(mTimeline->GetCurrentTimeAsDuration().Value());
   }
 
-  UpdateTiming(SeekFlag::NoSeek, SyncNotifyFlag::Async);
+  UpdateTiming(SeekFlag::NoSeek, SyncNotifyFlag::Sync);
 
   if (!mEffect) {
     return;
@@ -1179,7 +1179,7 @@ void Animation::ResumeAt(const TimeDuration& aReadyTime) {
 
   mPendingState = PendingState::NotPending;
 
-  UpdateTiming(SeekFlag::NoSeek, SyncNotifyFlag::Async);
+  UpdateTiming(SeekFlag::NoSeek, SyncNotifyFlag::Sync);
 
   // If we had a pending playback rate, we will have now applied it so we need
   // to notify observers.