diff --git a/source/simulation2/MessageTypes.h b/source/simulation2/MessageTypes.h
index 0f245aabe9..33a03d2e6a 100644
--- a/source/simulation2/MessageTypes.h
+++ b/source/simulation2/MessageTypes.h
@@ -33,8 +33,8 @@
 	virtual int GetType() const { return MT_##name; } \
 	virtual const char* GetScriptHandlerName() const { return "On" #name; } \
 	virtual const char* GetScriptGlobalHandlerName() const { return "OnGlobal" #name; } \
-	virtual jsval ToJSVal(ScriptInterface& scriptInterface) const; \
-	static CMessage* FromJSVal(ScriptInterface&, jsval val);
+	virtual JS::Value ToJSVal(ScriptInterface& scriptInterface) const; \
+	static CMessage* FromJSVal(ScriptInterface&, JS::HandleValue val);
 
 class SceneCollector;
 class CFrustum;
diff --git a/source/simulation2/scripting/MessageTypeConversions.cpp b/source/simulation2/scripting/MessageTypeConversions.cpp
index 116cda917c..d6a909dc9f 100644
--- a/source/simulation2/scripting/MessageTypeConversions.cpp
+++ b/source/simulation2/scripting/MessageTypeConversions.cpp
@@ -22,41 +22,38 @@
 #include "simulation2/MessageTypes.h"
 
 #define TOJSVAL_SETUP() \
-	JSObject* obj; \
-	{\
-	JSAutoRequest rq(scriptInterface.GetContext()); \
-	obj = JS_NewObject(scriptInterface.GetContext(), NULL, NULL, NULL); \
+	JSContext* cx = scriptInterface.GetContext(); \
+	JSAutoRequest rq(cx); \
+	JS::RootedObject obj(cx, JS_NewObject(cx, NULL, NULL, NULL)); \
 	if (!obj) \
-		return JSVAL_VOID; \
-	}
+		return JS::UndefinedValue();
 
 #define SET_MSG_PROPERTY(name) \
 	do { \
-		JSAutoRequest rq(scriptInterface.GetContext()); \
-		JSContext* cx = scriptInterface.GetContext(); \
 		JS::RootedValue prop(cx);\
 		ScriptInterface::ToJSVal(cx, &prop, this->name); \
 		if (! JS_SetProperty(cx, obj, #name, prop.address())) \
-			return JSVAL_VOID; \
+			return JS::UndefinedValue(); \
 	} while (0);
 
 #define FROMJSVAL_SETUP() \
-	if ( JSVAL_IS_PRIMITIVE(val)) \
+	JSContext* cx = scriptInterface.GetContext(); \
+	JSAutoRequest rq(cx); \
+	if (val.isPrimitive()) \
 		return NULL; \
-	JSObject* obj = JSVAL_TO_OBJECT(val); \
-	JS::RootedValue prop(scriptInterface.GetContext());
+	JS::RootedObject obj(cx, &val.toObject()); \
+	JS::RootedValue prop(cx);
 
 #define GET_MSG_PROPERTY(type, name) \
 	type name; \
 	{ \
-	JSAutoRequest rq(scriptInterface.GetContext()); \
-	if (! JS_GetProperty(scriptInterface.GetContext(), obj, #name, prop.address())) \
+	if (! JS_GetProperty(cx, obj, #name, prop.address())) \
 		return NULL; \
-	if (! ScriptInterface::FromJSVal(scriptInterface.GetContext(), prop, name)) \
+	if (! ScriptInterface::FromJSVal(cx, prop, name)) \
 		return NULL; \
 	}
 
-jsval CMessage::ToJSValCached(ScriptInterface& scriptInterface) const
+JS::Value CMessage::ToJSValCached(ScriptInterface& scriptInterface) const
 {
 	if (m_Cached.uninitialised())
 		m_Cached = CScriptValRooted(scriptInterface.GetContext(), ToJSVal(scriptInterface));
@@ -66,13 +63,13 @@ jsval CMessage::ToJSValCached(ScriptInterface& scriptInterface) const
 
 ////////////////////////////////
 
-jsval CMessageTurnStart::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageTurnStart::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageTurnStart::FromJSVal(ScriptInterface& UNUSED(scriptInterface), jsval UNUSED(val))
+CMessage* CMessageTurnStart::FromJSVal(ScriptInterface& UNUSED(scriptInterface), JS::HandleValue UNUSED(val))
 {
 	return new CMessageTurnStart();
 }
@@ -80,13 +77,13 @@ CMessage* CMessageTurnStart::FromJSVal(ScriptInterface& UNUSED(scriptInterface),
 ////////////////////////////////
 
 #define MESSAGE_1(name, t0, a0) \
-	jsval CMessage##name::ToJSVal(ScriptInterface& scriptInterface) const \
+	JS::Value CMessage##name::ToJSVal(ScriptInterface& scriptInterface) const \
 	{ \
 		TOJSVAL_SETUP(); \
 		SET_MSG_PROPERTY(a0); \
-		return OBJECT_TO_JSVAL(obj); \
+		return JS::ObjectValue(*obj); \
 	} \
-	CMessage* CMessage##name::FromJSVal(ScriptInterface& scriptInterface, jsval val) \
+	CMessage* CMessage##name::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val) \
 	{ \
 		FROMJSVAL_SETUP(); \
 		GET_MSG_PROPERTY(t0, a0); \
@@ -100,16 +97,16 @@ MESSAGE_1(Update_Final, fixed, turnLength)
 
 ////////////////////////////////
 
-jsval CMessageInterpolate::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageInterpolate::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(deltaSimTime);
 	SET_MSG_PROPERTY(offset);
 	SET_MSG_PROPERTY(deltaRealTime);
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageInterpolate::FromJSVal(ScriptInterface& scriptInterface, jsval val)
+CMessage* CMessageInterpolate::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val)
 {
 	FROMJSVAL_SETUP();
 	GET_MSG_PROPERTY(float, deltaSimTime);
@@ -120,13 +117,13 @@ CMessage* CMessageInterpolate::FromJSVal(ScriptInterface& scriptInterface, jsval
 
 ////////////////////////////////
 
-jsval CMessageRenderSubmit::ToJSVal(ScriptInterface& UNUSED(scriptInterface)) const
+JS::Value CMessageRenderSubmit::ToJSVal(ScriptInterface& UNUSED(scriptInterface)) const
 {
 	LOGWARNING(L"CMessageRenderSubmit::ToJSVal not implemented");
-	return JSVAL_VOID;
+	return JS::UndefinedValue();
 }
 
-CMessage* CMessageRenderSubmit::FromJSVal(ScriptInterface& UNUSED(scriptInterface), jsval UNUSED(val))
+CMessage* CMessageRenderSubmit::FromJSVal(ScriptInterface& UNUSED(scriptInterface), JS::HandleValue UNUSED(val))
 {
 	LOGWARNING(L"CMessageRenderSubmit::FromJSVal not implemented");
 	return NULL;
@@ -134,13 +131,13 @@ CMessage* CMessageRenderSubmit::FromJSVal(ScriptInterface& UNUSED(scriptInterfac
 
 ////////////////////////////////
 
-jsval CMessageProgressiveLoad::ToJSVal(ScriptInterface& UNUSED(scriptInterface)) const
+JS::Value CMessageProgressiveLoad::ToJSVal(ScriptInterface& UNUSED(scriptInterface)) const
 {
 	LOGWARNING(L"CMessageProgressiveLoad::ToJSVal not implemented");
-	return JSVAL_VOID;
+	return JS::UndefinedValue();
 }
 
-CMessage* CMessageProgressiveLoad::FromJSVal(ScriptInterface& UNUSED(scriptInterface), jsval UNUSED(val))
+CMessage* CMessageProgressiveLoad::FromJSVal(ScriptInterface& UNUSED(scriptInterface), JS::HandleValue UNUSED(val))
 {
 	LOGWARNING(L"CMessageProgressiveLoad::FromJSVal not implemented");
 	return NULL;
@@ -148,13 +145,13 @@ CMessage* CMessageProgressiveLoad::FromJSVal(ScriptInterface& UNUSED(scriptInter
 
 ////////////////////////////////
 
-jsval CMessageDeserialized::ToJSVal(ScriptInterface& UNUSED(scriptInterface)) const
+JS::Value CMessageDeserialized::ToJSVal(ScriptInterface& UNUSED(scriptInterface)) const
 {
 	LOGWARNING(L"CMessageDeserialized::ToJSVal not implemented");
-	return JSVAL_VOID;
+	return JS::UndefinedValue();
 }
 
-CMessage* CMessageDeserialized::FromJSVal(ScriptInterface& UNUSED(scriptInterface), jsval UNUSED(val))
+CMessage* CMessageDeserialized::FromJSVal(ScriptInterface& UNUSED(scriptInterface), JS::HandleValue UNUSED(val))
 {
 	LOGWARNING(L"CMessageDeserialized::FromJSVal not implemented");
 	return NULL;
@@ -162,14 +159,14 @@ CMessage* CMessageDeserialized::FromJSVal(ScriptInterface& UNUSED(scriptInterfac
 
 ////////////////////////////////
 
-jsval CMessageCreate::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageCreate::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(entity);
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageCreate::FromJSVal(ScriptInterface& scriptInterface, jsval val)
+CMessage* CMessageCreate::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val)
 {
 	FROMJSVAL_SETUP();
 	GET_MSG_PROPERTY(entity_id_t, entity);
@@ -178,14 +175,14 @@ CMessage* CMessageCreate::FromJSVal(ScriptInterface& scriptInterface, jsval val)
 
 ////////////////////////////////
 
-jsval CMessageDestroy::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageDestroy::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(entity);
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageDestroy::FromJSVal(ScriptInterface& scriptInterface, jsval val)
+CMessage* CMessageDestroy::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val)
 {
 	FROMJSVAL_SETUP();
 	GET_MSG_PROPERTY(entity_id_t, entity);
@@ -194,16 +191,16 @@ CMessage* CMessageDestroy::FromJSVal(ScriptInterface& scriptInterface, jsval val
 
 ////////////////////////////////
 
-jsval CMessageOwnershipChanged::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageOwnershipChanged::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(entity);
 	SET_MSG_PROPERTY(from);
 	SET_MSG_PROPERTY(to);
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageOwnershipChanged::FromJSVal(ScriptInterface& scriptInterface, jsval val)
+CMessage* CMessageOwnershipChanged::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val)
 {
 	FROMJSVAL_SETUP();
 	GET_MSG_PROPERTY(entity_id_t, entity);
@@ -214,7 +211,7 @@ CMessage* CMessageOwnershipChanged::FromJSVal(ScriptInterface& scriptInterface,
 
 ////////////////////////////////
 
-jsval CMessagePositionChanged::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessagePositionChanged::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(entity);
@@ -222,10 +219,10 @@ jsval CMessagePositionChanged::ToJSVal(ScriptInterface& scriptInterface) const
 	SET_MSG_PROPERTY(x);
 	SET_MSG_PROPERTY(z);
 	SET_MSG_PROPERTY(a);
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessagePositionChanged::FromJSVal(ScriptInterface& scriptInterface, jsval val)
+CMessage* CMessagePositionChanged::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val)
 {
 	FROMJSVAL_SETUP();
 	GET_MSG_PROPERTY(entity_id_t, entity);
@@ -238,13 +235,13 @@ CMessage* CMessagePositionChanged::FromJSVal(ScriptInterface& scriptInterface, j
 
 ////////////////////////////////
 
-jsval CMessageInterpolatedPositionChanged::ToJSVal(ScriptInterface& UNUSED(scriptInterface)) const
+JS::Value CMessageInterpolatedPositionChanged::ToJSVal(ScriptInterface& UNUSED(scriptInterface)) const
 {
 	LOGWARNING(L"CMessageInterpolatedPositionChanged::ToJSVal not implemented");
-	return JSVAL_VOID;
+	return JS::UndefinedValue();
 }
 
-CMessage* CMessageInterpolatedPositionChanged::FromJSVal(ScriptInterface& UNUSED(scriptInterface), jsval UNUSED(val))
+CMessage* CMessageInterpolatedPositionChanged::FromJSVal(ScriptInterface& UNUSED(scriptInterface), JS::HandleValue UNUSED(val))
 {
 	LOGWARNING(L"CMessageInterpolatedPositionChanged::FromJSVal not implemented");
 	return NULL;
@@ -252,15 +249,15 @@ CMessage* CMessageInterpolatedPositionChanged::FromJSVal(ScriptInterface& UNUSED
 
 ////////////////////////////////
 
-jsval CMessageTerritoryPositionChanged::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageTerritoryPositionChanged::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(entity);
 	SET_MSG_PROPERTY(newTerritory);
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageTerritoryPositionChanged::FromJSVal(ScriptInterface& scriptInterface, jsval val)
+CMessage* CMessageTerritoryPositionChanged::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val)
 {
 	FROMJSVAL_SETUP();
 	GET_MSG_PROPERTY(entity_id_t, entity);
@@ -270,15 +267,15 @@ CMessage* CMessageTerritoryPositionChanged::FromJSVal(ScriptInterface& scriptInt
 
 ////////////////////////////////
 
-jsval CMessageMotionChanged::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageMotionChanged::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(starting);
 	SET_MSG_PROPERTY(error);
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageMotionChanged::FromJSVal(ScriptInterface& scriptInterface, jsval val)
+CMessage* CMessageMotionChanged::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val)
 {
 	FROMJSVAL_SETUP();
 	GET_MSG_PROPERTY(bool, starting);
@@ -288,7 +285,7 @@ CMessage* CMessageMotionChanged::FromJSVal(ScriptInterface& scriptInterface, jsv
 
 ////////////////////////////////
 
-jsval CMessageTerrainChanged::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageTerrainChanged::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(i0);
@@ -298,7 +295,7 @@ jsval CMessageTerrainChanged::ToJSVal(ScriptInterface& scriptInterface) const
 	return OBJECT_TO_JSVAL(obj);
 }
 
-CMessage* CMessageTerrainChanged::FromJSVal(ScriptInterface& scriptInterface, jsval val)
+CMessage* CMessageTerrainChanged::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val)
 {
 	FROMJSVAL_SETUP();
 	GET_MSG_PROPERTY(int32_t, i0);
@@ -310,17 +307,17 @@ CMessage* CMessageTerrainChanged::FromJSVal(ScriptInterface& scriptInterface, js
 
 ////////////////////////////////
 
-jsval CMessageVisibilityChanged::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageVisibilityChanged::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(player);
 	SET_MSG_PROPERTY(ent);
 	SET_MSG_PROPERTY(oldVisibility);
 	SET_MSG_PROPERTY(newVisibility);
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageVisibilityChanged::FromJSVal(ScriptInterface& scriptInterface, jsval val)
+CMessage* CMessageVisibilityChanged::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val)
 {
 	FROMJSVAL_SETUP();
 	GET_MSG_PROPERTY(player_id_t, player);
@@ -332,55 +329,55 @@ CMessage* CMessageVisibilityChanged::FromJSVal(ScriptInterface& scriptInterface,
 
 ////////////////////////////////
 
-jsval CMessageWaterChanged::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageWaterChanged::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	return OBJECT_TO_JSVAL(obj);
 }
 
-CMessage* CMessageWaterChanged::FromJSVal(ScriptInterface& UNUSED(scriptInterface), jsval UNUSED(val))
+CMessage* CMessageWaterChanged::FromJSVal(ScriptInterface& UNUSED(scriptInterface), JS::HandleValue UNUSED(val))
 {
 	return new CMessageWaterChanged();
 }
 
 ////////////////////////////////
 
-jsval CMessageObstructionMapShapeChanged::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageObstructionMapShapeChanged::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageObstructionMapShapeChanged::FromJSVal(ScriptInterface& UNUSED(scriptInterface), jsval UNUSED(val))
+CMessage* CMessageObstructionMapShapeChanged::FromJSVal(ScriptInterface& UNUSED(scriptInterface), JS::HandleValue UNUSED(val))
 {
 	return new CMessageObstructionMapShapeChanged();
 }
 
 ////////////////////////////////
 
-jsval CMessageTerritoriesChanged::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageTerritoriesChanged::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageTerritoriesChanged::FromJSVal(ScriptInterface& UNUSED(scriptInterface), jsval UNUSED(val))
+CMessage* CMessageTerritoriesChanged::FromJSVal(ScriptInterface& UNUSED(scriptInterface), JS::HandleValue UNUSED(val))
 {
 	return new CMessageTerritoriesChanged();
 }
 
 ////////////////////////////////
 
-jsval CMessageRangeUpdate::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageRangeUpdate::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(tag);
 	SET_MSG_PROPERTY(added);
 	SET_MSG_PROPERTY(removed);
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageRangeUpdate::FromJSVal(ScriptInterface& UNUSED(scriptInterface), jsval UNUSED(val))
+CMessage* CMessageRangeUpdate::FromJSVal(ScriptInterface& UNUSED(scriptInterface), JS::HandleValue UNUSED(val))
 {
 	LOGWARNING(L"CMessageRangeUpdate::FromJSVal not implemented");
 	return NULL;
@@ -388,13 +385,13 @@ CMessage* CMessageRangeUpdate::FromJSVal(ScriptInterface& UNUSED(scriptInterface
 
 ////////////////////////////////
 
-jsval CMessagePathResult::ToJSVal(ScriptInterface& UNUSED(scriptInterface)) const
+JS::Value CMessagePathResult::ToJSVal(ScriptInterface& UNUSED(scriptInterface)) const
 {
 	LOGWARNING(L"CMessagePathResult::ToJSVal not implemented");
-	return JSVAL_VOID;
+	return JS::UndefinedValue();
 }
 
-CMessage* CMessagePathResult::FromJSVal(ScriptInterface& UNUSED(scriptInterface), jsval UNUSED(val))
+CMessage* CMessagePathResult::FromJSVal(ScriptInterface& UNUSED(scriptInterface), JS::HandleValue UNUSED(val))
 {
 	LOGWARNING(L"CMessagePathResult::FromJSVal not implemented");
 	return NULL;
@@ -402,16 +399,16 @@ CMessage* CMessagePathResult::FromJSVal(ScriptInterface& UNUSED(scriptInterface)
 
 ////////////////////////////////
 
-jsval CMessageValueModification::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageValueModification::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(entities);
 	SET_MSG_PROPERTY(component);
 	SET_MSG_PROPERTY(valueNames);
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageValueModification::FromJSVal(ScriptInterface& scriptInterface, jsval val)
+CMessage* CMessageValueModification::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val)
 {
 	FROMJSVAL_SETUP();
 	GET_MSG_PROPERTY(std::vector<entity_id_t>, entities);
@@ -422,16 +419,16 @@ CMessage* CMessageValueModification::FromJSVal(ScriptInterface& scriptInterface,
 
 ////////////////////////////////
 
-jsval CMessageTemplateModification::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageTemplateModification::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(player);
 	SET_MSG_PROPERTY(component);
 	SET_MSG_PROPERTY(valueNames);
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageTemplateModification::FromJSVal(ScriptInterface& scriptInterface, jsval val)
+CMessage* CMessageTemplateModification::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val)
 {
 	FROMJSVAL_SETUP();
 	GET_MSG_PROPERTY(player_id_t, player);
@@ -442,16 +439,16 @@ CMessage* CMessageTemplateModification::FromJSVal(ScriptInterface& scriptInterfa
 
 ////////////////////////////////
 
-jsval CMessageVisionRangeChanged::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageVisionRangeChanged::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
 	SET_MSG_PROPERTY(entity);
 	SET_MSG_PROPERTY(oldRange);
 	SET_MSG_PROPERTY(newRange);
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageVisionRangeChanged::FromJSVal(ScriptInterface& scriptInterface, jsval val)
+CMessage* CMessageVisionRangeChanged::FromJSVal(ScriptInterface& scriptInterface, JS::HandleValue val)
 {
 	FROMJSVAL_SETUP();
 	GET_MSG_PROPERTY(entity_id_t, entity);
@@ -462,20 +459,20 @@ CMessage* CMessageVisionRangeChanged::FromJSVal(ScriptInterface& scriptInterface
 
 ////////////////////////////////
 
-jsval CMessageMinimapPing::ToJSVal(ScriptInterface& scriptInterface) const
+JS::Value CMessageMinimapPing::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();
-	return OBJECT_TO_JSVAL(obj);
+	return JS::ObjectValue(*obj);
 }
 
-CMessage* CMessageMinimapPing::FromJSVal(ScriptInterface& UNUSED(scriptInterface), jsval UNUSED(val))
+CMessage* CMessageMinimapPing::FromJSVal(ScriptInterface& UNUSED(scriptInterface), JS::HandleValue UNUSED(val))
 {
 	return new CMessageMinimapPing();
 }
 
 ////////////////////////////////////////////////////////////////
 
-CMessage* CMessageFromJSVal(int mtid, ScriptInterface& scriptingInterface, jsval val)
+CMessage* CMessageFromJSVal(int mtid, ScriptInterface& scriptingInterface, JS::HandleValue val)
 {
 	switch (mtid)
 	{
diff --git a/source/simulation2/system/ComponentManager.cpp b/source/simulation2/system/ComponentManager.cpp
index 4129de5e7a..eca5c0b659 100644
--- a/source/simulation2/system/ComponentManager.cpp
+++ b/source/simulation2/system/ComponentManager.cpp
@@ -42,8 +42,8 @@ public:
 	virtual const char* GetScriptGlobalHandlerName() const { return globalHandlerName.c_str(); }
 	virtual jsval ToJSVal(ScriptInterface& UNUSED(scriptInterface)) const { return msg.get(); }
 
-	CMessageScripted(int mtid, const std::string& name, const CScriptValRooted& msg) :
-		mtid(mtid), handlerName("On" + name), globalHandlerName("OnGlobal" + name), msg(msg)
+	CMessageScripted(ScriptInterface& scriptInterface, int mtid, const std::string& name, JS::HandleValue msg) :
+		mtid(mtid), handlerName("On" + name), globalHandlerName("OnGlobal" + name), msg(scriptInterface.GetContext(), msg)
 	{
 	}
 
@@ -416,25 +416,29 @@ std::vector<IComponent*> CComponentManager::Script_GetComponentsWithInterface(Sc
 	return ret;
 }
 
-CMessage* CComponentManager::ConstructMessage(int mtid, CScriptVal data)
+CMessage* CComponentManager::ConstructMessage(int mtid, JS::HandleValue data)
 {
 	if (mtid == MT__Invalid || mtid > (int)m_MessageTypeIdsByName.size()) // (IDs start at 1 so use '>' here)
 		LOGERROR(L"PostMessage with invalid message type ID '%d'", mtid);
 
 	if (mtid < MT__LastNative)
 	{
-		return CMessageFromJSVal(mtid, m_ScriptInterface, data.get());
+		return CMessageFromJSVal(mtid, m_ScriptInterface, data);
 	}
 	else
 	{
-		return new CMessageScripted(mtid, m_MessageTypeNamesById[mtid],
-				CScriptValRooted(m_ScriptInterface.GetContext(), data));
+		return new CMessageScripted(m_ScriptInterface, mtid, m_MessageTypeNamesById[mtid], data);
 	}
 }
 
-void CComponentManager::Script_PostMessage(ScriptInterface::CxPrivate* pCxPrivate, int ent, int mtid, CScriptVal data)
+void CComponentManager::Script_PostMessage(ScriptInterface::CxPrivate* pCxPrivate, int ent, int mtid, CScriptVal data1)
 {
 	CComponentManager* componentManager = static_cast<CComponentManager*> (pCxPrivate->pCBData);
+	
+	JSContext* cx = componentManager->GetScriptInterface().GetContext();
+	JSAutoRequest rq(cx);
+	// TODO: With ESR31 we should be able to take JS::HandleValue directly
+	JS::RootedValue data(cx, data1.get());
 
 	CMessage* msg = componentManager->ConstructMessage(mtid, data);
 	if (!msg)
@@ -445,9 +449,14 @@ void CComponentManager::Script_PostMessage(ScriptInterface::CxPrivate* pCxPrivat
 	delete msg;
 }
 
-void CComponentManager::Script_BroadcastMessage(ScriptInterface::CxPrivate* pCxPrivate, int mtid, CScriptVal data)
+void CComponentManager::Script_BroadcastMessage(ScriptInterface::CxPrivate* pCxPrivate, int mtid, CScriptVal data1)
 {
 	CComponentManager* componentManager = static_cast<CComponentManager*> (pCxPrivate->pCBData);
+	
+	JSContext* cx = componentManager->GetScriptInterface().GetContext();
+	JSAutoRequest rq(cx);
+	// TODO: With ESR31 we should be able to take JS::HandleValue directly
+	JS::RootedValue data(cx, data1.get());
 
 	CMessage* msg = componentManager->ConstructMessage(mtid, data);
 	if (!msg)
diff --git a/source/simulation2/system/ComponentManager.h b/source/simulation2/system/ComponentManager.h
index 69a0c7b3bc..5b936a0847 100644
--- a/source/simulation2/system/ComponentManager.h
+++ b/source/simulation2/system/ComponentManager.h
@@ -291,7 +291,7 @@ private:
 	// callback function to handle recursively finding files in a directory
 	static Status FindJSONFilesCallback(const VfsPath&, const CFileInfo&, const uintptr_t);
 
-	CMessage* ConstructMessage(int mtid, CScriptVal data);
+	CMessage* ConstructMessage(int mtid, JS::HandleValue data);
 	void SendGlobalMessage(entity_id_t ent, const CMessage& msg);
 
 	void FlattenDynamicSubscriptions();
diff --git a/source/simulation2/system/Message.h b/source/simulation2/system/Message.h
index 4a18fde615..553363101b 100644
--- a/source/simulation2/system/Message.h
+++ b/source/simulation2/system/Message.h
@@ -31,14 +31,14 @@ public:
 	virtual int GetType() const = 0;
 	virtual const char* GetScriptHandlerName() const = 0;
 	virtual const char* GetScriptGlobalHandlerName() const = 0;
-	virtual jsval ToJSVal(ScriptInterface&) const = 0;
-	jsval ToJSValCached(ScriptInterface&) const;
+	virtual JS::Value ToJSVal(ScriptInterface&) const = 0;
+	JS::Value ToJSValCached(ScriptInterface&) const;
 private:
 	mutable CScriptValRooted m_Cached;
 };
 // TODO: GetType could be replaced with a plain member variable to avoid some
 // virtual calls, if that turns out to be worthwhile
 
-CMessage* CMessageFromJSVal(int mtid, ScriptInterface&, jsval);
+CMessage* CMessageFromJSVal(int mtid, ScriptInterface&, JS::HandleValue);
 
 #endif // INCLUDED_MESSAGE