diff --git a/src/applib/command_executor_gui.cpp b/src/applib/command_executor_gui.cpp
index d9f3f40..ba1bebc 100644
--- a/src/applib/command_executor_gui.cpp
+++ b/src/applib/command_executor_gui.cpp
@@ -152,9 +152,9 @@ bool CommandExecutorGui::execute_tick_func(TickStatus status)
 
 		// If quit() was called during one of the manual iterations, and execute()
 		// is called in a loop, we need to prevent any real execution past that point.
-		if (Gtk::Main::iteration(false) && Gtk::Main::level() > 0) {
-			return false;  // try to abort execution
-		}
+		// if (Gtk::Main::iteration(false) && Gtk::Main::level() > 0) {
+		// 	return false;  // try to abort execution
+		// }
 
 		execution_running_ = true;
 		should_abort_ = false;
@@ -181,14 +181,14 @@ bool CommandExecutorGui::execute_tick_func(TickStatus status)
 
 	if (status == TickStatus::running) {
 
-		while (Gtk::Main::events_pending()) {
-			// Gtk::Main::iteration() returns true if Gtk::Main::quit() has been called, or if there's no Main yet.
-			// debug_out_dump("app", Gtk::Main::level() << "\n");
-			if (Gtk::Main::iteration() && Gtk::Main::level() > 0) {
-				set_running_dialog_abort_mode(true);
-				return false;  // try to abort execution
-			}
-		}
+		// while (Gtk::Main::events_pending()) {
+		// 	// Gtk::Main::iteration() returns true if Gtk::Main::quit() has been called, or if there's no Main yet.
+		// 	// debug_out_dump("app", Gtk::Main::level() << "\n");
+		// 	if (Gtk::Main::iteration() && Gtk::Main::level() > 0) {
+		// 		set_running_dialog_abort_mode(true);
+		// 		return false;  // try to abort execution
+		// 	}
+		// }
 
 		if (should_abort_) {
 			should_abort_ = false;
@@ -205,9 +205,9 @@ bool CommandExecutorGui::execute_tick_func(TickStatus status)
 
 
 	if (status == TickStatus::stopping) {
-		if (Gtk::Main::iteration(false) && Gtk::Main::level() > 0) {
-			return false;  // we're exiting from the main loop, so return early
-		}
+		// if (Gtk::Main::iteration(false) && Gtk::Main::level() > 0) {
+		// 	return false;  // we're exiting from the main loop, so return early
+		// }
 
 		// show a dialog with "Aborting..."
 		this->update_dialog_show_timer();
diff --git a/src/applib/examples/example_smartctl_executor.cpp b/src/applib/examples/example_smartctl_executor.cpp
index 6314d4d..f225c9e 100644
--- a/src/applib/examples/example_smartctl_executor.cpp
+++ b/src/applib/examples/example_smartctl_executor.cpp
@@ -25,7 +25,8 @@ int main(int argc, char** argv)
 {
 	return hz::main_exception_wrapper([&argc, &argv]()
 	{
-		Gtk::Main m(argc, argv);
+		// Required by executor
+		auto app = Gtk::Application::create("org.gsmartcontrol.examples.smartctl_executor");
 
 		// NOTE: Don't use long options (e.g. --info). Use short ones (e.g. -i),
 		// because long options may be unsupported on some platforms.
diff --git a/src/gsc_init.cpp b/src/gsc_init.cpp
index 08967d9..437785e 100644
--- a/src/gsc_init.cpp
+++ b/src/gsc_init.cpp
@@ -323,13 +323,16 @@ bool app_init_and_loop(int& argc, char**& argv)
 	// Note that changing GTK locale after it's inited isn't really supported by GTK,
 	// but we have no other choice - glib needs system locale when parsing the
 	// arguments, and gtk is inited while the parsing is performed.
+#if GTK_CHECK_VERSION(4, 0, 0)
+	Glib::set_init_to_users_preferred_locale(args.arg_locale == TRUE);
+#else
 	if (args.arg_locale == FALSE) {
 		hz::locale_c_set("C");
 	} else {
 		// change the C++ locale to match the C one.
 		hz::locale_cpp_set("");  // this may fail on some systems
 	}
-
+#endif
 
 	if (args.arg_version == TRUE) {
 		// show version information and exit
@@ -410,23 +413,25 @@ bool app_init_and_loop(int& argc, char**& argv)
 				| G_LOG_FLAG_RECURSION), glib_message_handler, nullptr);
 	}
 
-
+#if !GTK_CHECK_VERSION(4, 0, 0)
 	// Save the locale
 	std::locale final_loc_cpp = hz::locale_cpp_get<std::locale>();
+#endif
 
-	// Initialize GTK+ (it's already initialized by command-line parser,
-	// so this doesn't do much).
+	// Initialize GTK+.
+	// GTKMM 3 Notes (no longer valid as of gtkmm4):
 	// Newer gtkmm will try to set the C++ locale here.
 	// Note: passing false (as use_locale) as the third parameter here
 	// will generate a gtk_disable_setlocale() warning (due to gtk being
 	// already initialized), so manually save / restore the C++ locale
 	// (C locale won't be touched).
 	// Nothing is affected in gtkmm itself by C++ locale, so it's ok to do it.
-	Gtk::Main m(argc, argv);
+	auto app = Gtk::Application::create("org.gsmartcontrol.base");
 
+#if !GTK_CHECK_VERSION(4, 0, 0)
 	// Restore the locale
 	hz::locale_cpp_set(final_loc_cpp);
-
+#endif
 
 	debug_out_info("app", "Current C locale: " << hz::locale_c_get() << "\n");
 	debug_out_info("app", "Current C++ locale: " << hz::locale_cpp_get<std::string>() << "\n");
@@ -553,7 +558,7 @@ bool app_init_and_loop(int& argc, char**& argv)
 
 		// The Main Loop
 		debug_out_info("app", "Entering main loop.\n");
-		Gtk::Main::run();
+		app->run(argc, argv);
 		debug_out_info("app", "Main loop exited.\n");
 	}
 
@@ -578,7 +583,7 @@ void app_quit()
 	// exit the main loop
 	debug_out_info("app", "Trying to exit the main loop...\n");
 
-	Gtk::Main::quit();
+	Gtk::Application::get_default()->quit();
 
 	// don't destroy main window here - we may be in one of its callbacks
 }