diff --git a/libs/gtkmm2ext/gtkapplication_quartz.mm b/libs/gtkmm2ext/gtkapplication_quartz.mm
index 8baafadc7d..38db6a2d42 100644
--- a/libs/gtkmm2ext/gtkapplication_quartz.mm
+++ b/libs/gtkmm2ext/gtkapplication_quartz.mm
@@ -1468,6 +1468,9 @@ namespace Gtk {
 - (NSApplicationTerminateReply) applicationShouldTerminate:(NSApplication *) app
 {
 	UNUSED_PARAMETER(app);
+	if (_modal_state) {
+		return NSTerminateCancel;
+	}
 	Gtkmm2ext::Application::instance()->ShouldQuit ();
 	return NSTerminateCancel;
 }