diff --git a/spa/include/spa/buffer/meta.h b/spa/include/spa/buffer/meta.h
index 1c1089633..952e79366 100644
--- a/spa/include/spa/buffer/meta.h
+++ b/spa/include/spa/buffer/meta.h
@@ -41,7 +41,7 @@ enum spa_meta_type {
 	SPA_META_Invalid,
 	SPA_META_Header,	/**< struct spa_meta_header */
 	SPA_META_VideoCrop,	/**< struct spa_meta_region with cropping data */
-	SPA_META_VideoDamage,	/**< array of struct spa_meta_region with damage */
+	SPA_META_VideoDamage,	/**< array of struct spa_meta_region with damage, where an invalid entry or end-of-array marks the end. */
 	SPA_META_Bitmap,	/**< struct spa_meta_bitmap */
 	SPA_META_Cursor,	/**< struct spa_meta_cursor */
 	SPA_META_Control,	/**< metadata contains a spa_meta_control