diff --git a/src/platformtheme/qdbusmenubar.cpp b/src/platformtheme/qdbusmenubar.cpp
--- a/src/platformtheme/qdbusmenubar.cpp
+++ b/src/platformtheme/qdbusmenubar.cpp
@@ -156,7 +156,7 @@
         return;
 
     QDBusMenuRegistrarInterface registrar(REGISTRAR_SERVICE, REGISTRAR_PATH, connection, this);
-    QDBusPendingReply<> r = registrar.RegisterWindow(static_cast<uint>(window()->winId()), QDBusObjectPath(m_objectPath));
+    QDBusPendingReply<> r = registrar.RegisterWindow(static_cast<uint>(m_window->winId()), QDBusObjectPath(m_objectPath));
     r.waitForFinished();
     if (r.isError()) {
         qWarning("Failed to register window menu, reason: %s (\"%s\")",
@@ -171,7 +171,7 @@
 
     if (m_window) {
         QDBusMenuRegistrarInterface registrar(REGISTRAR_SERVICE, REGISTRAR_PATH, connection, this);
-        QDBusPendingReply<> r = registrar.UnregisterWindow(static_cast<uint>(window()->winId()));
+        QDBusPendingReply<> r = registrar.UnregisterWindow(static_cast<uint>(m_window->winId()));
         r.waitForFinished();
         if (r.isError())
             qWarning("Failed to unregister window menu, reason: %s (\"%s\")",