Index: ps/trunk/source/scriptinterface/ScriptInterface.h
===================================================================
--- ps/trunk/source/scriptinterface/ScriptInterface.h
+++ ps/trunk/source/scriptinterface/ScriptInterface.h
@@ -135,8 +135,8 @@
 
 	/**
 	 * Set the named property on the global object.
-	 * If @p replace is true, an existing property will be overwritten; otherwise attempts
-	 * to set an already-defined value will fail.
+	 * Optionally makes it {ReadOnly, DontEnum}. We do not allow to make it DontDelete, so that it can be hotloaded
+	 * by deleting it and re-creating it, which is done by setting @p replace to true.
 	 */
 	template<typename T>
 	bool SetGlobal(const char* name, const T& value, bool replace = false, bool constant = true, bool enumerate = true);
@@ -360,9 +360,9 @@
 	bool Eval_(const char* code, JS::MutableHandleValue ret) const;
 	bool Eval_(const wchar_t* code, JS::MutableHandleValue ret) const;
 	bool SetGlobal_(const char* name, JS::HandleValue value, bool replace, bool constant, bool enumerate);
-	bool SetProperty_(JS::HandleValue obj, const char* name, JS::HandleValue value, bool readonly, bool enumerate) const;
-	bool SetProperty_(JS::HandleValue obj, const wchar_t* name, JS::HandleValue value, bool readonly, bool enumerate) const;
-	bool SetPropertyInt_(JS::HandleValue obj, int name, JS::HandleValue value, bool readonly, bool enumerate) const;
+	bool SetProperty_(JS::HandleValue obj, const char* name, JS::HandleValue value, bool constant, bool enumerate) const;
+	bool SetProperty_(JS::HandleValue obj, const wchar_t* name, JS::HandleValue value, bool constant, bool enumerate) const;
+	bool SetPropertyInt_(JS::HandleValue obj, int name, JS::HandleValue value, bool constant, bool enumerate) const;
 	bool GetProperty_(JS::HandleValue obj, const char* name, JS::MutableHandleValue out) const;
 	bool GetPropertyInt_(JS::HandleValue obj, int name, JS::MutableHandleValue value) const;
 	static bool IsExceptionPending(JSContext* cx);
@@ -494,30 +494,30 @@
 }
 
 template<typename T>
-bool ScriptInterface::SetProperty(JS::HandleValue obj, const char* name, const T& value, bool readonly, bool enumerate) const
+bool ScriptInterface::SetProperty(JS::HandleValue obj, const char* name, const T& value, bool constant, bool enumerate) const
 {
 	JSAutoRequest rq(GetContext());
 	JS::RootedValue val(GetContext());
 	AssignOrToJSVal(GetContext(), &val, value);
-	return SetProperty_(obj, name, val, readonly, enumerate);
+	return SetProperty_(obj, name, val, constant, enumerate);
 }
 
 template<typename T>
-bool ScriptInterface::SetProperty(JS::HandleValue obj, const wchar_t* name, const T& value, bool readonly, bool enumerate) const
+bool ScriptInterface::SetProperty(JS::HandleValue obj, const wchar_t* name, const T& value, bool constant, bool enumerate) const
 {
 	JSAutoRequest rq(GetContext());
 	JS::RootedValue val(GetContext());
 	AssignOrToJSVal(GetContext(), &val, value);
-	return SetProperty_(obj, name, val, readonly, enumerate);
+	return SetProperty_(obj, name, val, constant, enumerate);
 }
 
 template<typename T>
-bool ScriptInterface::SetPropertyInt(JS::HandleValue obj, int name, const T& value, bool readonly, bool enumerate) const
+bool ScriptInterface::SetPropertyInt(JS::HandleValue obj, int name, const T& value, bool constant, bool enumerate) const
 {
 	JSAutoRequest rq(GetContext());
 	JS::RootedValue val(GetContext());
 	AssignOrToJSVal(GetContext(), &val, value);
-	return SetPropertyInt_(obj, name, val, readonly, enumerate);
+	return SetPropertyInt_(obj, name, val, constant, enumerate);
 }
 
 template<typename T>
Index: ps/trunk/source/scriptinterface/ScriptInterface.cpp
===================================================================
--- ps/trunk/source/scriptinterface/ScriptInterface.cpp
+++ ps/trunk/source/scriptinterface/ScriptInterface.cpp
@@ -589,21 +589,40 @@
 {
 	JSAutoRequest rq(m->m_cx);
 	JS::RootedObject global(m->m_cx, m->m_glob);
-	if (!replace)
+
+	bool found;
+	if (!JS_HasProperty(m->m_cx, global, name, &found))
+		return false;
+	if (found)
 	{
-		bool found;
-		if (!JS_HasProperty(m->m_cx, global, name, &found))
+		JS::Rooted<JSPropertyDescriptor> desc(m->m_cx);
+		if (!JS_GetOwnPropertyDescriptor(m->m_cx, global, name, &desc))
 			return false;
-		if (found)
+
+		if (desc.isReadonly())
 		{
-			JS_ReportError(m->m_cx, "SetGlobal \"%s\" called multiple times", name);
-			return false;
+			if (!replace)
+			{
+				JS_ReportError(m->m_cx, "SetGlobal \"%s\" called multiple times", name);
+				return false;
+			}
+
+			// This is not supposed to happen, unless the user has called SetProperty with constant = true on the global object
+			// instead of using SetGlobal.
+			if (desc.isPermanent())
+			{
+				JS_ReportError(m->m_cx, "The global \"%s\" is permanent and cannot be hotloaded", name);
+				return false;
+			}
+
+			LOGMESSAGE("Hotloading new value for global \"%s\".", name);
+			ENSURE(JS_DeleteProperty(m->m_cx, global, name));
 		}
 	}
 
 	uint attrs = 0;
 	if (constant)
-		attrs |= JSPROP_READONLY | JSPROP_PERMANENT;
+		attrs |= JSPROP_READONLY;
 	if (enumerate)
 		attrs |= JSPROP_ENUMERATE;
 
Index: ps/trunk/source/simulation2/system/ComponentManager.cpp
===================================================================
--- ps/trunk/source/simulation2/system/ComponentManager.cpp
+++ ps/trunk/source/simulation2/system/ComponentManager.cpp
@@ -145,6 +145,8 @@
 		return false;
 	std::string content = file.DecodeUTF8(); // assume it's UTF-8
 	bool ok = m_ScriptInterface.LoadScript(filename, content);
+
+	m_CurrentlyHotloading = false;
 	return ok;
 }
 
@@ -374,9 +376,6 @@
 void CComponentManager::Script_RegisterGlobal(ScriptInterface::CxPrivate* pCxPrivate, const std::string& name, JS::HandleValue value)
 {
 	CComponentManager* componentManager = static_cast<CComponentManager*> (pCxPrivate->pCBData);
-
-	// Set the value, and accept duplicates only if hotloading (otherwise it's an error,
-	// in order to detect accidental duplicate definitions of globals)
 	componentManager->m_ScriptInterface.SetGlobal(name.c_str(), value, componentManager->m_CurrentlyHotloading);
 }