diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index b4be9bbfe76..99a6a24afff 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -1246,6 +1246,7 @@ void QWidgetPrivate::create()
     // in case the extra was already valid.
     if (!win) {
         createTLSysExtra();
+        Q_ASSERT(topData()->window);
         win = topData()->window;
     }