diff --git a/gtk2_ardour/route_ui.cc b/gtk2_ardour/route_ui.cc
index 6b879755c6..0d8a8963eb 100644
--- a/gtk2_ardour/route_ui.cc
+++ b/gtk2_ardour/route_ui.cc
@@ -2069,6 +2069,10 @@ RouteUI::setup_invert_buttons ()
 void
 RouteUI::update_polarity_display ()
 {
+	if (!_route) {
+		return;
+	}
+
 	uint32_t const N = _route->phase_control()->size();
 	if (N > _max_invert_buttons) {