diff --git a/gtk2_ardour/bundle_manager.cc b/gtk2_ardour/bundle_manager.cc
index d8cfde7123..e6260ae4d0 100644
--- a/gtk2_ardour/bundle_manager.cc
+++ b/gtk2_ardour/bundle_manager.cc
@@ -112,6 +112,17 @@ BundleEditorMatrix::can_add_channels (boost::shared_ptr<Bundle> b) const
 	return PortMatrix::can_add_channels (b);
 }
 
+bool
+BundleEditorMatrix::can_add_port (boost::shared_ptr<Bundle> b, DataType t) const
+{
+#if 1
+	return true; // anything goes
+#else
+	/* Do not allow to mix datatypes */
+	return _bundle->nchannels().get (t) > 0;
+#endif
+}
+
 void
 BundleEditorMatrix::add_channel (boost::shared_ptr<Bundle> b, DataType t)
 {
@@ -136,11 +147,10 @@ BundleEditorMatrix::add_channel (boost::shared_ptr<Bundle> b, DataType t)
 bool
 BundleEditorMatrix::can_remove_channels (boost::shared_ptr<Bundle> b) const
 {
-	if (b == _bundle) {
-		return true;
+	if (b != _bundle) {
+		return false;
 	}
-
-	return PortMatrix::can_remove_channels (b);
+	return _bundle->n_total () > 1;
 }
 
 void
diff --git a/gtk2_ardour/bundle_manager.h b/gtk2_ardour/bundle_manager.h
index fc365a0992..38294cd8c0 100644
--- a/gtk2_ardour/bundle_manager.h
+++ b/gtk2_ardour/bundle_manager.h
@@ -44,6 +44,7 @@ public:
 	PortMatrixNode::State get_state (ARDOUR::BundleChannel c[2]) const;
 
 	bool can_add_channels (boost::shared_ptr<ARDOUR::Bundle>) const;
+	bool can_add_port (boost::shared_ptr<ARDOUR::Bundle>, ARDOUR::DataType t) const;
 
 	void add_channel (boost::shared_ptr<ARDOUR::Bundle>, ARDOUR::DataType);
 	bool can_remove_channels (boost::shared_ptr<ARDOUR::Bundle>) const;
diff --git a/gtk2_ardour/port_matrix.cc b/gtk2_ardour/port_matrix.cc
index 353c510b55..e064d0aabd 100644
--- a/gtk2_ardour/port_matrix.cc
+++ b/gtk2_ardour/port_matrix.cc
@@ -460,7 +460,7 @@ PortMatrix::popup_menu (BundleChannel column, BundleChannel row, uint32_t t)
 			if (can_add_channels (bc[dim].bundle)) {
 				/* Start off with options for the `natural' port type */
 				for (DataType::iterator i = DataType::begin(); i != DataType::end(); ++i) {
-					if (should_show (*i) && can_add_channel_proxy (w, *i)) {
+					if (should_show (*i) && can_add_port_proxy (w, *i)) {
 						snprintf (buf, sizeof (buf), _("Add %s %s"), (*i).to_i18n_string(), channel_noun().c_str());
 						sub.push_back (MenuElem (buf, sigc::bind (sigc::mem_fun (*this, &PortMatrix::add_channel_proxy), w, *i)));
 					}
@@ -468,7 +468,7 @@ PortMatrix::popup_menu (BundleChannel column, BundleChannel row, uint32_t t)
 
 				/* Now add other ones */
 				for (DataType::iterator i = DataType::begin(); i != DataType::end(); ++i) {
-					if (!should_show (*i) && can_add_channel_proxy (w, *i)) {
+					if (!should_show (*i) && can_add_port_proxy (w, *i)) {
 						snprintf (buf, sizeof (buf), _("Add %s %s"), (*i).to_i18n_string(), channel_noun().c_str());
 						sub.push_back (MenuElem (buf, sigc::bind (sigc::mem_fun (*this, &PortMatrix::add_channel_proxy), w, *i)));
 					}
@@ -735,6 +735,13 @@ PortMatrix::can_add_channels (boost::shared_ptr<Bundle> b) const
 	return io_from_bundle (b) != 0;
 }
 
+bool
+PortMatrix::can_add_port (boost::shared_ptr<Bundle> b, DataType t) const
+{
+	boost::shared_ptr<IO> io = io_from_bundle (b);
+	return io && io->can_add_port (t);
+}
+
 void
 PortMatrix::add_channel (boost::shared_ptr<Bundle> b, DataType t)
 {
@@ -805,14 +812,13 @@ PortMatrix::remove_all_channels (boost::weak_ptr<Bundle> w)
 }
 
 bool
-PortMatrix::can_add_channel_proxy (boost::weak_ptr<Bundle> w, DataType t) const
+PortMatrix::can_add_port_proxy (boost::weak_ptr<Bundle> w, DataType t) const
 {
 	boost::shared_ptr<Bundle> b = w.lock ();
 	if (!b) {
 		return false;
 	}
-	boost::shared_ptr<IO> io = io_from_bundle (b);
-	return io && io->can_add_port (t);
+	return can_add_port (b, t);
 }
 
 void
diff --git a/gtk2_ardour/port_matrix.h b/gtk2_ardour/port_matrix.h
index 8667c8c8e6..24f1a6961f 100644
--- a/gtk2_ardour/port_matrix.h
+++ b/gtk2_ardour/port_matrix.h
@@ -153,6 +153,7 @@ public:
 	virtual bool can_rename_channels (boost::shared_ptr<ARDOUR::Bundle>) const {
 		return false;
 	}
+	virtual bool can_add_port (boost::shared_ptr<ARDOUR::Bundle>, ARDOUR::DataType t) const;
 	virtual void rename_channel (ARDOUR::BundleChannel) {}
 	virtual std::string disassociation_verb () const = 0;
 	virtual std::string channel_noun () const;
@@ -183,7 +184,7 @@ private:
 	void routes_changed ();
 	void reconnect_to_routes ();
 	void select_arrangement ();
-	bool can_add_channel_proxy (boost::weak_ptr<ARDOUR::Bundle>, ARDOUR::DataType) const;
+	bool can_add_port_proxy (boost::weak_ptr<ARDOUR::Bundle>, ARDOUR::DataType) const;
 	void add_channel_proxy (boost::weak_ptr<ARDOUR::Bundle>, ARDOUR::DataType);
 	void remove_channel_proxy (boost::weak_ptr<ARDOUR::Bundle>, uint32_t);
 	void rename_channel_proxy (boost::weak_ptr<ARDOUR::Bundle>, uint32_t);