diff --git a/app_win_2_back.cpp b/app_win_2_back.cpp
index ff5dac1..aa743ed 100644
--- a/app_win_2_back.cpp
+++ b/app_win_2_back.cpp
@@ -112,8 +112,10 @@ namespace gui_to_app {
     void AppWin2Back::on_quit() noexcept {
         auto windows = get_windows();
         for (auto *window: windows) {
-            window->set_visible(false);
-            delete window;
+            if (window != nullptr) {
+                window->set_visible(false);
+                delete window;
+            }
         }
         quit();
     }