diff --git a/source/simulation2/components/CCmpAIManager.cpp b/source/simulation2/components/CCmpAIManager.cpp
index 2e52a4b791..369f7d6280 100644
--- a/source/simulation2/components/CCmpAIManager.cpp
+++ b/source/simulation2/components/CCmpAIManager.cpp
@@ -563,9 +563,10 @@ public:
 		JS::RootedValue tmpEntityTemplates(cx); // TODO: Check if this temporary root can be removed after SpiderMonkey 31 upgrade 
 		m_ScriptInterface->Eval("({})", &tmpEntityTemplates);
 
+		JS::RootedValue val(cx);
 		for (size_t i = 0; i < templates.size(); ++i)
 		{
-			JS::RootedValue val(cx, templates[i].second->ToJSVal(cx, false));
+			templates[i].second->ToJSVal(cx, false, &val);
 			m_ScriptInterface->SetProperty(tmpEntityTemplates, templates[i].first.c_str(), val, true);
 		}
 
diff --git a/source/simulation2/scripting/EngineScriptConversions.cpp b/source/simulation2/scripting/EngineScriptConversions.cpp
index d107977ead..2f907a3e54 100644
--- a/source/simulation2/scripting/EngineScriptConversions.cpp
+++ b/source/simulation2/scripting/EngineScriptConversions.cpp
@@ -67,7 +67,7 @@ template<> void ScriptInterface::ToJSVal<IComponent*>(JSContext* cx, JS::Mutable
 template<> void ScriptInterface::ToJSVal<CParamNode>(JSContext* cx, JS::MutableHandleValue ret, CParamNode const& val)
 {
 	JSAutoRequest rq(cx);
-	ret.set(val.ToJSVal(cx, true));
+	val.ToJSVal(cx, true, ret);
 
 	// Prevent modifications to the object, so that it's safe to share between
 	// components and to reconstruct on deserialization
diff --git a/source/simulation2/system/ParamNode.cpp b/source/simulation2/system/ParamNode.cpp
index fcd0c82775..f966004b10 100644
--- a/source/simulation2/system/ParamNode.cpp
+++ b/source/simulation2/system/ParamNode.cpp
@@ -308,63 +308,85 @@ void CParamNode::ToXML(std::wostream& strm) const
 	}
 }
 
-jsval CParamNode::ToJSVal(JSContext* cx, bool cacheValue) const
+void CParamNode::ToJSVal(JSContext* cx, bool cacheValue, JS::MutableHandleValue ret) const
 {
 	if (cacheValue && !m_ScriptVal.uninitialised())
-		return m_ScriptVal.get();
+	{
+		ret.set(m_ScriptVal.get());
+		return;
+	}
 
-	jsval val = ConstructJSVal(cx);
+	ConstructJSVal(cx, ret);
 
 	if (cacheValue)
-		m_ScriptVal = CScriptValRooted(cx, val);
-
-	return val;
+		m_ScriptVal = CScriptValRooted(cx, ret);
 }
 
-jsval CParamNode::ConstructJSVal(JSContext* cx) const
+void CParamNode::ConstructJSVal(JSContext* cx, JS::MutableHandleValue ret) const
 {
 	JSAutoRequest rq(cx);
 	if (m_Childs.empty())
 	{
 		// Empty node - map to undefined
 		if (m_Value.empty())
-			return JSVAL_VOID;
+		{
+			ret.setUndefined();
+			return;
+		}
 
 		// Just a string
 		utf16string text(m_Value.begin(), m_Value.end());
-		JSString* str = JS_InternUCStringN(cx, reinterpret_cast<const jschar*>(text.data()), text.length());
+		JS::RootedString str(cx, JS_InternUCStringN(cx, reinterpret_cast<const jschar*>(text.data()), text.length()));
 		if (str)
-			return STRING_TO_JSVAL(str);
+		{
+			ret.setString(str);
+			return;
+		}
 		// TODO: report error
-		return JSVAL_VOID;
+		ret.setUndefined();
+		return;
 	}
 
 	// Got child nodes - convert this node into a hash-table-style object:
 
-	JSObject* obj = JS_NewObject(cx, NULL, NULL, NULL);
+	JS::RootedObject obj(cx, JS_NewObject(cx, NULL, NULL, NULL));
 	if (!obj)
-		return JSVAL_VOID; // TODO: report error
+	{
+		ret.setUndefined();
+		return; // TODO: report error
+	}
 
+	JS::RootedValue childVal(cx);
 	for (std::map<std::string, CParamNode>::const_iterator it = m_Childs.begin(); it != m_Childs.end(); ++it)
 	{
-		JS::RootedValue childVal(cx, it->second.ConstructJSVal(cx));
+		it->second.ConstructJSVal(cx, &childVal);
 		if (!JS_SetProperty(cx, obj, it->first.c_str(), childVal.address()))
-			return JSVAL_VOID; // TODO: report error
+		{
+			ret.setUndefined();
+			return; // TODO: report error
+		}
 	}
 
 	// If the node has a string too, add that as an extra property
 	if (!m_Value.empty())
 	{
 		utf16string text(m_Value.begin(), m_Value.end());
-		JSString* str = JS_InternUCStringN(cx, reinterpret_cast<const jschar*>(text.data()), text.length());
+		JS::RootedString str(cx, JS_InternUCStringN(cx, reinterpret_cast<const jschar*>(text.data()), text.length()));
 		if (!str)
-			return JSVAL_VOID; // TODO: report error
-		JS::RootedValue childVal(cx, STRING_TO_JSVAL(str));
+		{
+			ret.setUndefined();
+			return; // TODO: report error
+		}
+		
+		JS::RootedValue childVal(cx, JS::StringValue(str));
 		if (!JS_SetProperty(cx, obj, "_string", childVal.address()))
-			return JSVAL_VOID; // TODO: report error
+		{
+			ret.setUndefined();
+			return; // TODO: report error
+		}
 	}
 
-	return OBJECT_TO_JSVAL(obj);
+	ret.setObject(*obj);
 }
 
 void CParamNode::ResetScriptVal()
diff --git a/source/simulation2/system/ParamNode.h b/source/simulation2/system/ParamNode.h
index 8f0d7d56bc..fda6a5ed71 100644
--- a/source/simulation2/system/ParamNode.h
+++ b/source/simulation2/system/ParamNode.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2010 Wildfire Games.
+/* Copyright (C) 2014 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -220,7 +220,7 @@ public:
 	 * The cache will be reset if *this* node is modified (e.g. by LoadXML),
 	 * but *not* if any child nodes are modified (so don't do that).
 	 */
-	jsval ToJSVal(JSContext* cx, bool cacheValue) const;
+	void ToJSVal(JSContext* cx, bool cacheValue, JS::MutableHandleValue ret) const;
 
 	/**
 	 * Returns the names/nodes of the children of this node, ordered by name
@@ -247,7 +247,7 @@ private:
 
 	void ResetScriptVal();
 
-	jsval ConstructJSVal(JSContext* cx) const;
+	void ConstructJSVal(JSContext* cx, JS::MutableHandleValue ret) const;
 
 	std::wstring m_Value;
 	ChildrenMap m_Childs;