diff --git a/components/script/task_queue.rs b/components/script/task_queue.rs
index 4b489b7eec496..1fac477865ed9 100644
--- a/components/script/task_queue.rs
+++ b/components/script/task_queue.rs
@@ -237,7 +237,7 @@ impl<T: QueuedTaskConversion> TaskQueue<T> {
                             // Reduce the length of throttles,
                             // but don't add the task to "msg_queue",
                             // and neither increment "taken_task_counter".
-                            throttled_length - =1;
+                            throttled_length -= 1;
                             continue;
                         }
                     }