diff --git a/src/widgets/widgets/qmainwindowlayout.cpp b/src/widgets/widgets/qmainwindowlayout.cpp
index 1cc7f201ba..8f8642a72a 100644
--- a/src/widgets/widgets/qmainwindowlayout.cpp
+++ b/src/widgets/widgets/qmainwindowlayout.cpp
@@ -68,7 +68,7 @@
 
 QT_BEGIN_NAMESPACE
 
-#ifndef QT_NO_DOCKWIDGET
+#ifdef QT_NO_DOCKWIDGET
 extern QMainWindowLayout *qt_mainwindow_layout(const QMainWindow *window);
 #endif