diff --git a/libs/ardour/ardour/luaproc.h b/libs/ardour/ardour/luaproc.h
index fa8a826778..d2acc9600d 100644
--- a/libs/ardour/ardour/luaproc.h
+++ b/libs/ardour/ardour/luaproc.h
@@ -78,6 +78,8 @@ public:
 
 	PluginOutputConfiguration possible_output () const { return _output_configs; }
 
+	void drop_references ();
+
 	std::set<Evoral::Parameter> automatable() const;
 
 	void activate () { }
diff --git a/libs/ardour/ardour/plugin.h b/libs/ardour/ardour/plugin.h
index a062cc8858..5653a8bc0d 100644
--- a/libs/ardour/ardour/plugin.h
+++ b/libs/ardour/ardour/plugin.h
@@ -106,6 +106,8 @@ public:
 		activate ();
 	}
 
+	virtual void drop_references () {}
+
 	virtual std::set<Evoral::Parameter> automatable () const                   = 0;
 	virtual std::string                 describe_parameter (Evoral::Parameter) = 0;
 	virtual std::string                 state_node_name () const               = 0;
diff --git a/libs/ardour/ardour/plugin_insert.h b/libs/ardour/ardour/plugin_insert.h
index f627184a05..200edf0d4c 100644
--- a/libs/ardour/ardour/plugin_insert.h
+++ b/libs/ardour/ardour/plugin_insert.h
@@ -61,6 +61,8 @@ public:
 	PluginInsert (Session&, boost::shared_ptr<Plugin> = boost::shared_ptr<Plugin>());
 	~PluginInsert ();
 
+	void drop_references ();
+
 	static const std::string port_automation_node_name;
 
 	int set_state(const XMLNode&, int version);
diff --git a/libs/ardour/luaproc.cc b/libs/ardour/luaproc.cc
index a1bbd1c5c9..ba388a2569 100644
--- a/libs/ardour/luaproc.cc
+++ b/libs/ardour/luaproc.cc
@@ -130,7 +130,7 @@ LuaProc::~LuaProc () {
 				_stats_max[1] * (float)_stats_cnt / _stats_avg[1]);
 	}
 #endif
-	lua.do_command ("collectgarbage();");
+	lua.collect_garbage ();
 	delete (_lua_dsp);
 	delete (_lua_latency);
 	delete [] _control_data;
@@ -182,6 +182,12 @@ LuaProc::init ()
 	lua.do_command ("function ardour () end");
 }
 
+void
+LuaProc::drop_references ()
+{
+	lua.collect_garbage ();
+}
+
 boost::weak_ptr<Route>
 LuaProc::route () const
 {
diff --git a/libs/ardour/plugin_insert.cc b/libs/ardour/plugin_insert.cc
index 47c5faf3dc..a654f2b625 100644
--- a/libs/ardour/plugin_insert.cc
+++ b/libs/ardour/plugin_insert.cc
@@ -110,6 +110,15 @@ PluginInsert::~PluginInsert ()
 	}
 }
 
+void
+PluginInsert::drop_references ()
+{
+	for (Plugins::iterator i = _plugins.begin(); i != _plugins.end(); ++i) {
+		(*i)->drop_references ();
+	}
+	Processor::drop_references ();
+}
+
 void
 PluginInsert::set_strict_io (bool b)
 {