diff --git a/gtk2_ardour/global_port_matrix.cc b/gtk2_ardour/global_port_matrix.cc
index fcd9960e43..8c1fde3082 100644
--- a/gtk2_ardour/global_port_matrix.cc
+++ b/gtk2_ardour/global_port_matrix.cc
@@ -192,6 +192,15 @@ GlobalPortMatrixWindow::set_session (Session* s)
 	}
 }
 
+void
+GlobalPortMatrix::set_session (Session *s)
+{
+	SessionHandlePtr::set_session (s);
+	if (!s) return;
+	setup_all_ports ();
+	init();
+}
+
 string
 GlobalPortMatrix::disassociation_verb () const
 {
diff --git a/gtk2_ardour/global_port_matrix.h b/gtk2_ardour/global_port_matrix.h
index 1dabcbd379..d45a639093 100644
--- a/gtk2_ardour/global_port_matrix.h
+++ b/gtk2_ardour/global_port_matrix.h
@@ -31,6 +31,7 @@ public:
 	GlobalPortMatrix (Gtk::Window*, ARDOUR::Session*, ARDOUR::DataType);
 
 	void setup_ports (int);
+	void set_session (ARDOUR::Session* s);
 
 	void set_state (ARDOUR::BundleChannel c[2], bool);
 	PortMatrixNode::State get_state (ARDOUR::BundleChannel c[2]) const;