diff --git a/libs/ardour/route_dag.cc b/libs/ardour/route_dag.cc
index 6a6e8d2bbd..3b13cf9415 100644
--- a/libs/ardour/route_dag.cc
+++ b/libs/ardour/route_dag.cc
@@ -146,7 +146,9 @@ struct RouteRecEnabledComparator
 	}
 };
 
-		
+/** Perform a topological sort of a list of routes using a directed graph representing connections.
+ *  @return Sorted list of routes, or 0 if the graph contains cycles (feedback loops).
+ */
 boost::shared_ptr<RouteList>
 ARDOUR::topological_sort (
 	boost::shared_ptr<RouteList> routes,
@@ -189,7 +191,8 @@ ARDOUR::topological_sort (
 	}
 
 	if (!edges.empty ()) {
-		cout << "Feedback detected.\n";
+		/* There are cycles in the graph, so we can't do a topological sort */
+		return boost::shared_ptr<RouteList> ();
 	}
 
 	return sorted_routes;