diff --git a/src/v0.rs b/src/v0.rs
index 78e0893..e5a5507 100644
--- a/src/v0.rs
+++ b/src/v0.rs
@@ -434,6 +434,7 @@ pub struct SettingEvent{
 }
 
 /// A segment of event timelines.
+/// Timelines are always be sorted.
 #[derive(Default)]
 pub struct Block{
 	pub input_events:Vec<Timed<InputEvent>>,