diff --git a/src/frontend/menu.cpp b/src/frontend/menu.cpp
index 64f8affb..1e279ae4 100644
--- a/src/frontend/menu.cpp
+++ b/src/frontend/menu.cpp
@@ -86,25 +86,25 @@ bool menus::call(Engine& engine, runnable func) {
         engine.setScreen(std::make_shared<MenuScreen>(engine));
         // could not to find or read pack
         guiutil::alert(
-            gui, langs::get(L"error.pack-not-found")+L": "+
+            gui->getMenu(), langs::get(L"error.pack-not-found")+L": "+
             util::str2wstr_utf8(error.getPackId())
         );
         return false;
     } catch (const assetload::error& error) {
         engine.setScreen(std::make_shared<MenuScreen>(engine));
         guiutil::alert(
-            gui, langs::get(L"Assets Load Error", L"menu")+L":\n"+
+            gui->getMenu(), langs::get(L"Assets Load Error", L"menu")+L":\n"+
             util::str2wstr_utf8(error.what())
         );
         return false;
     } catch (const parsing_error& error) {
         engine.setScreen(std::make_shared<MenuScreen>(engine));
-        guiutil::alert(gui, util::str2wstr_utf8(error.errorLog()));
+        guiutil::alert(gui->getMenu(), util::str2wstr_utf8(error.errorLog()));
         return false;
     } catch (const std::runtime_error& error) {
         engine.setScreen(std::make_shared<MenuScreen>(engine));
         guiutil::alert(
-            gui, langs::get(L"Content Error", L"menu")+L":\n"+
+            gui->getMenu(), langs::get(L"Content Error", L"menu")+L":\n"+
             util::str2wstr_utf8(error.what())
         );
         return false;
diff --git a/src/graphics/ui/gui_util.cpp b/src/graphics/ui/gui_util.cpp
index 95e37514..0d913395 100644
--- a/src/graphics/ui/gui_util.cpp
+++ b/src/graphics/ui/gui_util.cpp
@@ -23,8 +23,11 @@ std::shared_ptr<gui::UINode> guiutil::create(const std::string& source, scripten
     return reader.readXML("[string]", source);
 }
 
-void guiutil::alert(GUI* gui, const std::wstring& text, const runnable& on_hidden) {
-    auto menu = gui->getMenu();
+void guiutil::alert(
+    const std::shared_ptr<gui::Menu>& menu,
+    const std::wstring& text,
+    const runnable& on_hidden
+) {
     auto panel = std::make_shared<Panel>(glm::vec2(500, 300), glm::vec4(8.0f), 8.0f);
     panel->setColor(glm::vec4(0.0f, 0.0f, 0.0f, 0.5f));
     
@@ -47,7 +50,7 @@ void guiutil::alert(GUI* gui, const std::wstring& text, const runnable& on_hidde
 }
 
 void guiutil::confirm(
-        GUI* gui, 
+        const std::shared_ptr<gui::Menu>& menu, 
         const std::wstring& text, 
         const runnable& on_confirm,
         std::wstring yestext, 
@@ -55,7 +58,6 @@ void guiutil::confirm(
     if (yestext.empty()) yestext = langs::get(L"Yes");
     if (notext.empty()) notext = langs::get(L"No");
 
-    auto menu = gui->getMenu();
     auto panel = std::make_shared<Panel>(glm::vec2(600, 200), glm::vec4(8.0f), 8.0f);
     panel->setColor(glm::vec4(0.0f, 0.0f, 0.0f, 0.5f));
     panel->add(std::make_shared<Label>(text));
@@ -79,8 +81,8 @@ void guiutil::confirm(
     menu->setPage("<confirm>");
 }
 
-void guiutil::confirmWithMemo(
-        gui::GUI* gui, 
+void guiutil::confirm_with_memo(
+        const std::shared_ptr<gui::Menu>& menu,
         const std::wstring& text, 
         const std::wstring& memo,
         const runnable& on_confirm,
@@ -90,7 +92,6 @@ void guiutil::confirmWithMemo(
     if (yestext.empty()) yestext = langs::get(L"Yes");
     if (notext.empty()) notext = langs::get(L"No");
 
-    auto menu = gui->getMenu();
     auto panel = std::make_shared<Panel>(glm::vec2(600, 500), glm::vec4(8.0f), 8.0f);
     panel->setColor(glm::vec4(0.0f, 0.0f, 0.0f, 0.5f));
     panel->add(std::make_shared<Label>(text));
diff --git a/src/graphics/ui/gui_util.hpp b/src/graphics/ui/gui_util.hpp
index 7f8d750e..65264877 100644
--- a/src/graphics/ui/gui_util.hpp
+++ b/src/graphics/ui/gui_util.hpp
@@ -13,20 +13,20 @@ namespace guiutil {
     std::shared_ptr<gui::UINode> create(const std::string& source, scriptenv env=0);
 
     void alert(
-        gui::GUI* gui, 
+        const std::shared_ptr<gui::Menu>& menu,
         const std::wstring& text, 
         const runnable& on_hidden=nullptr
     );
 
     void confirm(
-        gui::GUI* gui, 
+        const std::shared_ptr<gui::Menu>& menu,
         const std::wstring& text, 
         const runnable& on_confirm=nullptr,
         std::wstring yestext=L"", 
         std::wstring notext=L"");
 
-    void confirmWithMemo(
-        gui::GUI* gui, 
+    void confirm_with_memo(
+        const std::shared_ptr<gui::Menu>& menu,
         const std::wstring& text, 
         const std::wstring& memo,
         const runnable& on_confirm=nullptr,
diff --git a/src/logic/EngineController.cpp b/src/logic/EngineController.cpp
index c6c1f480..3c9fa093 100644
--- a/src/logic/EngineController.cpp
+++ b/src/logic/EngineController.cpp
@@ -33,7 +33,7 @@ EngineController::EngineController(Engine& engine) : engine(engine) {
 void EngineController::deleteWorld(const std::string& name) {
     fs::path folder = engine.getPaths().getWorldFolderByName(name);
     guiutil::confirm(
-        engine.getGUI(),
+        engine.getGUI()->getMenu(),
         langs::get(L"delete-confirm", L"world") + L" (" +
             util::str2wstr_utf8(folder.u8string()) + L")",
         [=]() {
@@ -100,8 +100,8 @@ static void show_convert_request(
         for (const auto& line : report->getDataLoss()) {
             text += util::str2wstr_utf8(line) + L"\n";
         }
-        guiutil::confirmWithMemo(
-            engine.getGUI(),
+        guiutil::confirm_with_memo(
+            engine.getGUI()->getMenu(),
             langs::get(message),
             text,
             on_confirm,
@@ -111,7 +111,7 @@ static void show_convert_request(
         return;
     }
     guiutil::confirm(
-        engine.getGUI(),
+        engine.getGUI()->getMenu(),
         langs::get(message),
         on_confirm,
         L"",
@@ -156,7 +156,7 @@ static void load_world(
         engine.onWorldOpen(std::move(level));
     } catch (const world_load_error& error) {
         guiutil::alert(
-            engine.getGUI(),
+            engine.getGUI()->getMenu(),
             langs::get(L"Error") + L": " + util::str2wstr_utf8(error.what())
         );
         return;
@@ -326,7 +326,7 @@ void EngineController::reconfigPacks(
 
     if (hasIndices) {
         guiutil::confirm(
-            engine.getGUI(),
+            engine.getGUI()->getMenu(),
             langs::get(L"remove-confirm", L"pack") + L" (" +
                 util::str2wstr_utf8(ss.str()) + L")",
             [=]() { removeFunc(); }
diff --git a/src/logic/scripting/lua/libs/libcore.cpp b/src/logic/scripting/lua/libs/libcore.cpp
index 37944694..ebf363ab 100644
--- a/src/logic/scripting/lua/libs/libcore.cpp
+++ b/src/logic/scripting/lua/libs/libcore.cpp
@@ -100,32 +100,23 @@ static int l_delete_world(lua::State* L) {
 /// @param remPacks An array of packs to remove
 static int l_reconfig_packs(lua::State* L) {
     if (!lua::istable(L, 1)) {
-        throw std::runtime_error("strings array expected as the first argument"
-        );
+        throw std::runtime_error("strings array expected as the first argument");
     }
     if (!lua::istable(L, 2)) {
-        throw std::runtime_error("strings array expected as the second argument"
-        );
+        throw std::runtime_error("strings array expected as the second argument");
     }
     std::vector<std::string> addPacks;
-    if (!lua::istable(L, 1)) {
-        throw std::runtime_error("an array expected as argument 1");
-    }
     int addLen = lua::objlen(L, 1);
     for (int i = 0; i < addLen; i++) {
         lua::rawgeti(L, i + 1, 1);
-        addPacks.emplace_back(lua::tostring(L, -1));
+        addPacks.emplace_back(lua::require_lstring(L, -1));
         lua::pop(L);
     }
-
     std::vector<std::string> remPacks;
-    if (!lua::istable(L, 2)) {
-        throw std::runtime_error("an array expected as argument 2");
-    }
     int remLen = lua::objlen(L, 2);
     for (int i = 0; i < remLen; i++) {
         lua::rawgeti(L, i + 1, 2);
-        remPacks.emplace_back(lua::tostring(L, -1));
+        remPacks.emplace_back(lua::require_lstring(L, -1));
         lua::pop(L);
     }
     auto engineController = engine->getController();