diff --git a/source/scriptinterface/ScriptVal.cpp b/source/scriptinterface/ScriptVal.cpp
index 93eb66a1c5..b62ce51a75 100644
--- a/source/scriptinterface/ScriptVal.cpp
+++ b/source/scriptinterface/ScriptVal.cpp
@@ -52,5 +52,9 @@ jsval CScriptValRooted::get() const
 bool CScriptValRooted::undefined() const
 {
 	return (!m_Val || *m_Val == JSVAL_VOID);
-
+}
+
+bool CScriptValRooted::uninitialised() const
+{
+	return !m_Val;
 }
diff --git a/source/scriptinterface/ScriptVal.h b/source/scriptinterface/ScriptVal.h
index 772be08e24..8a7c3b8222 100644
--- a/source/scriptinterface/ScriptVal.h
+++ b/source/scriptinterface/ScriptVal.h
@@ -49,6 +49,8 @@ public:
 
 	bool undefined() const;
 
+	bool uninitialised() const;
+
 private:
 	boost::shared_ptr<jsval> m_Val;
 };
diff --git a/source/simulation2/scripting/MessageTypeConversions.cpp b/source/simulation2/scripting/MessageTypeConversions.cpp
index 660e6805d8..e9f31d650c 100644
--- a/source/simulation2/scripting/MessageTypeConversions.cpp
+++ b/source/simulation2/scripting/MessageTypeConversions.cpp
@@ -50,6 +50,14 @@ jsval prop;
 	if (! ScriptInterface::FromJSVal(scriptInterface.GetContext(), prop, name)) \
 		return NULL;
 
+jsval CMessage::ToJSValCached(ScriptInterface& scriptInterface) const
+{
+	if (m_Cached.uninitialised())
+		m_Cached = CScriptValRooted(scriptInterface.GetContext(), ToJSVal(scriptInterface));
+
+	return m_Cached.get();
+}
+
 ////////////////////////////////
 
 jsval CMessageTurnStart::ToJSVal(ScriptInterface& UNUSED(scriptInterface)) const
diff --git a/source/simulation2/scripting/ScriptComponent.cpp b/source/simulation2/scripting/ScriptComponent.cpp
index f6f96da1d1..e896275e11 100644
--- a/source/simulation2/scripting/ScriptComponent.cpp
+++ b/source/simulation2/scripting/ScriptComponent.cpp
@@ -53,9 +53,7 @@ void CComponentTypeScript::HandleMessage(const CSimContext& UNUSED(context), con
 {
 	const char* name = global ? msg.GetScriptGlobalHandlerName() : msg.GetScriptHandlerName();
 
-	CScriptVal msgVal = msg.ToJSVal(m_ScriptInterface);
-	// TODO: repeated conversions are exceedingly inefficient. Should
-	// cache this once per message (if it's used by >= 1 scripted component)
+	CScriptVal msgVal = msg.ToJSValCached(m_ScriptInterface);
 
 	if (!m_ScriptInterface.CallFunctionVoid(m_Instance, name, msgVal))
 		LOGERROR(L"Script message handler %hs failed", name);