diff --git a/src/app.rs b/src/app.rs
index 8bf7164..7b68e38 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -563,8 +563,9 @@ pub trait App: 'static
 
 	/// Called every time a buffer for the main surface has been rendered and
 	/// committed, before the subsurfaces are reconciled for the same
-	/// iteration. Lets a host retire or mount a subsurface in the same flush
-	/// as the main frame it replaces, so the swap lands in one frame.
+	/// iteration. Lets a host sequence a subsurface change after the main
+	/// frame it depends on: a subsurface retired here goes away only once
+	/// the main frame that replaces it has been sent.
 	fn on_main_frame_committed( &mut self ) {}
 
 	/// Called when the surface is asked to close (compositor request, titlebar button,