diff --git a/libs/ardour/route.cc b/libs/ardour/route.cc
index 106cf7dba9..757d304611 100644
--- a/libs/ardour/route.cc
+++ b/libs/ardour/route.cc
@@ -5325,6 +5325,7 @@ Route::setup_invisible_processors ()
 		}
 #endif
 		if ((*i)->display_to_user ()) {
+			/* visible processor, put it on the list of new processors */
 			new_processors.push_back (*i);
 		}
 		else if (auxsnd && auxsnd->is_foldback ()) {