diff --git a/libs/ardour/port_manager.cc b/libs/ardour/port_manager.cc
index 03c3a31000..697476d90f 100644
--- a/libs/ardour/port_manager.cc
+++ b/libs/ardour/port_manager.cc
@@ -1005,7 +1005,9 @@ PortManager::connect_callback (const string& a, const string& b, bool conn)
 	}
 
 	if (!port_a && !port_b && Config->get_restore_hardware_connections () && !AudioEngine::instance ()->is_jack ()) {
-		AudioEngine::instance ()->session ()->set_dirty ();
+		if (AudioEngine::instance ()->session ()) {
+			AudioEngine::instance ()->session ()->set_dirty ();
+		}
 	}
 
 	PortConnectedOrDisconnected (