Index: source/scriptinterface/FunctionWrapper.h
===================================================================
--- source/scriptinterface/FunctionWrapper.h
+++ source/scriptinterface/FunctionWrapper.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2023 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -234,10 +234,9 @@
 		if (!JS_ValueToObject(rq.cx, val, &obj) || !obj)
 			return false;
 
-		// Check that the named function actually exists, to avoid ugly JS error reports
-		// when calling an undefined value
-		bool found;
-		if (!JS_HasProperty(rq.cx, obj, name, &found) || !found)
+		// Fetch the property explicitly - this avoids converting the arguments if it doesn't exist.
+		JS::RootedValue func(rq.cx);
+		if (!JS_GetProperty(rq.cx, obj, name, &func))
 			return false;
 
 		JS::RootedValueVector argv(rq.cx);
@@ -246,11 +245,11 @@
 
 		bool success;
 		if constexpr (std::is_same_v<R, JS::MutableHandleValue>)
-			success = JS_CallFunctionName(rq.cx, obj, name, argv, ret);
+			success = JS_CallFunctionValue(rq.cx, obj, func, argv, ret);
 		else
 		{
 			JS::RootedValue jsRet(rq.cx);
-			success = JS_CallFunctionName(rq.cx, obj, name, argv, &jsRet);
+			success = JS_CallFunctionValue(rq.cx, obj, func, argv, &jsRet);
 			if constexpr (!std::is_same_v<R, IgnoreResult_t>)
 			{
 				if (success)
Index: source/simulation2/scripting/MessageTypeConversions.cpp
===================================================================
--- source/simulation2/scripting/MessageTypeConversions.cpp
+++ source/simulation2/scripting/MessageTypeConversions.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2023 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -50,9 +50,8 @@
 		return NULL; \
 	}
 
-JS::Value CMessage::ToJSValCached(const ScriptInterface& scriptInterface) const
+JS::Value CMessage::ToJSValCached(const ScriptRequest& rq, const ScriptInterface& scriptInterface) const
 {
-	ScriptRequest rq(scriptInterface);
 	if (!m_Cached)
 		m_Cached.reset(new JS::PersistentRootedValue(rq.cx, ToJSVal(scriptInterface)));
 
Index: source/simulation2/scripting/ScriptComponent.cpp
===================================================================
--- source/simulation2/scripting/ScriptComponent.cpp
+++ source/simulation2/scripting/ScriptComponent.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2023 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -52,7 +52,7 @@
 
 	const char* name = global ? msg.GetScriptGlobalHandlerName() : msg.GetScriptHandlerName();
 
-	JS::RootedValue msgVal(rq.cx, msg.ToJSValCached(m_ScriptInterface));
+	JS::RootedValue msgVal(rq.cx, msg.ToJSValCached(rq, m_ScriptInterface));
 
 	if (!ScriptFunction::CallVoid(rq, m_Instance, name, msgVal))
 		LOGERROR("Script message handler %s failed", name);
Index: source/simulation2/system/Message.h
===================================================================
--- source/simulation2/system/Message.h
+++ source/simulation2/system/Message.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2020 Wildfire Games.
+/* Copyright (C) 2023 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -20,6 +20,8 @@
 
 #include "scriptinterface/ScriptTypes.h"
 
+class ScriptRequest;
+
 class CMessage
 {
 	NONCOPYABLE(CMessage);
@@ -31,7 +33,7 @@
 	virtual const char* GetScriptHandlerName() const = 0;
 	virtual const char* GetScriptGlobalHandlerName() const = 0;
 	virtual JS::Value ToJSVal(const ScriptInterface&) const = 0;
-	JS::Value ToJSValCached(const ScriptInterface&) const;
+	JS::Value ToJSValCached(const ScriptRequest& rq, const ScriptInterface&) const;
 private:
 	mutable std::unique_ptr<JS::PersistentRootedValue> m_Cached;
 };