diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index 34ac683e233e..ad90cc73b31d 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -948,7 +948,7 @@ impl Window {
         self.current_state.set(WindowState::Zombie);
         *self.js_runtime.borrow_mut() = None;
         self.browsing_context.set(None);
-        self.ignore_further_async_events.store(true, Ordering::Relaxed);
+        self.ignore_further_async_events.store(true, Ordering::SeqCst);
     }
 
     /// https://drafts.csswg.org/cssom-view/#dom-window-scroll
diff --git a/components/script/script_thread.rs b/components/script/script_thread.rs
index e115d0869565..e116ace1be41 100644
--- a/components/script/script_thread.rs
+++ b/components/script/script_thread.rs
@@ -190,7 +190,7 @@ pub struct CancellableRunnable<T: Runnable + Send> {
 
 impl<T: Runnable + Send> Runnable for CancellableRunnable<T> {
     fn is_cancelled(&self) -> bool {
-        self.cancelled.load(Ordering::Relaxed)
+        self.cancelled.load(Ordering::SeqCst)
     }
 
     fn handler(self: Box<CancellableRunnable<T>>) {