diff --git a/applets/appmenu/plugin/appmenumodel.cpp b/applets/appmenu/plugin/appmenumodel.cpp
--- a/applets/appmenu/plugin/appmenumodel.cpp
+++ b/applets/appmenu/plugin/appmenumodel.cpp
@@ -260,7 +260,14 @@
 {
     if (m_currentWindowId == id) {
         KWindowInfo info(id, NET::WMState | NET::WMGeometry);
-        const bool contained = m_screenGeometry.isNull() || m_screenGeometry.contains(info.geometry().center());
+
+        //! HACK: if the user has enabled PLASMA_USE_QT_SCALING under X11 environment
+        //! then the window and screen geometries can not be trusted for comparison.
+        //! In such case the global menu should be shown at all cases and not become hidden
+        //! from geometries comparison.
+        //! BUG: 404500
+        const bool untrustedGeometries = KWindowSystem::isPlatformX11() && qEnvironmentVariableIsSet("PLASMA_USE_QT_SCALING");
+        const bool contained = m_screenGeometry.isNull() || m_screenGeometry.contains(info.geometry().center()) || untrustedGeometries;
 
         setVisible(contained && !info.isMinimized());
     }