diff --git a/include/wlr/backend.h b/include/wlr/backend.h
index fdcc4ad5c..ad8070c23 100644
--- a/include/wlr/backend.h
+++ b/include/wlr/backend.h
@@ -25,6 +25,9 @@ struct wlr_backend_output_state {
 
 /**
  * A backend provides a set of input and output devices.
+ *
+ * Buffer capabilities and features can change over the lifetime of a backend,
+ * for instance when a child backend is added to a multi-backend.
  */
 struct wlr_backend {
 	const struct wlr_backend_impl *impl;