diff -r -u -X exclude ardour.org/branches/2.0-ongoing/gtk2_ardour/mixer_strip.cc branches/2.0-ongoing/gtk2_ardour/mixer_strip.cc
--- ardour.org/branches/2.0-ongoing/gtk2_ardour/mixer_strip.cc	2007-11-04 17:16:46.000000000 +0000
+++ branches/2.0-ongoing/gtk2_ardour/mixer_strip.cc	2007-11-04 17:30:27.000000000 +0000
@@ -243,7 +243,13 @@
 
 	width_hide_box.pack_start (width_button, false, true);
 	width_hide_box.pack_start (top_event_box, true, true);
-	width_hide_box.pack_end (hide_button, false, true);
+
+	if (!in_mixer || (!_route->master() && !_route->control())) {
+		/* we don't allow master or control routes to be hidden, unless
+		   we're the editor mix strip */
+		width_hide_box.pack_end (hide_button, false, true);
+	}
+	
 	Gtk::Alignment *gain_meter_alignment = Gtk::manage(new Gtk::Alignment());
 	gain_meter_alignment->set_padding(0, 4, 0, 0);
 	gain_meter_alignment->add(gpm);