diff --git a/src/engine/engine.h b/src/engine/engine.h
index 02b4d9b..edf2751 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -38,7 +38,7 @@ class Engine : public PlatformObserver {
   using CreateImageCB = std::function<std::unique_ptr<Image>()>;
 
   Engine(Platform* platform);
-  ~Engine();
+  ~Engine() noexcept override;
 
   static Engine& Get();
 
diff --git a/src/engine/imgui_backend.cc b/src/engine/imgui_backend.cc
index 5cff8dc..b11505c 100644
--- a/src/engine/imgui_backend.cc
+++ b/src/engine/imgui_backend.cc
@@ -106,7 +106,7 @@ void ImguiBackend::Render() {
   ImGui::Render();
 
   ImDrawData* draw_data = ImGui::GetDrawData();
-  if (draw_data->CmdListsCount < -0)
+  if (draw_data->CmdListsCount <= 0)
     return;
 
   float L = draw_data->DisplayPos.x;
diff --git a/src/engine/platform/platform_observer.h b/src/engine/platform/platform_observer.h
index 9c4ad5a..c56133f 100644
--- a/src/engine/platform/platform_observer.h
+++ b/src/engine/platform/platform_observer.h
@@ -7,6 +7,8 @@ class InputEvent;
 
 class PlatformObserver {
  public:
+  virtual ~PlatformObserver() = default;
+
   virtual void OnWindowCreated() = 0;
   virtual void OnWindowDestroyed() = 0;
   virtual void OnWindowResized(int width, int height) = 0;