diff --git a/libs/ardour/session_process.cc b/libs/ardour/session_process.cc
index e989671b0b..c50223f5a2 100644
--- a/libs/ardour/session_process.cc
+++ b/libs/ardour/session_process.cc
@@ -758,9 +758,18 @@ Session::process_audition (pframes_t nframes)
 	SessionEvent* ev;
 	boost::shared_ptr<RouteList> r = routes.reader ();
 
-	for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
-		if (!(*i)->is_auditioner()) {
-			(*i)->silence (nframes);
+	boost::shared_ptr<GraphChain> graph_chain = _graph_chain;
+	if (graph_chain) {
+		/* Ideally we'd use Session::rt_tasklist, since dependency is irrelevant.
+		 * However the RTTaskList process threads have no ProcessThread buffers
+		 * nor a SessioEvent thread_pool.
+		 */
+		_process_graph->silence_routes (graph_chain, nframes);
+	} else {
+		for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+			if (!(*i)->is_auditioner()) {
+				(*i)->silence (nframes);
+			}
 		}
 	}