diff --git a/libs/ardour/plugin_insert.cc b/libs/ardour/plugin_insert.cc
index c63066154a..5fbda57d58 100644
--- a/libs/ardour/plugin_insert.cc
+++ b/libs/ardour/plugin_insert.cc
@@ -112,7 +112,7 @@ PluginInsert::~PluginInsert ()
 void
 PluginInsert::set_strict_io (bool b)
 {
-	if (_plugins.front()->connect_all_audio_outputs ()) {
+	if (!_plugins.empty() && _plugins.front()->connect_all_audio_outputs ()) {
 		/* Ignore route setting, allow plugin to add/remove ports */
 		b = false;
 	}