diff --git a/src/corelib/global/qnamespace.h b/src/corelib/global/qnamespace.h
index 70f13cf79f..4a663fc8a5 100644
--- a/src/corelib/global/qnamespace.h
+++ b/src/corelib/global/qnamespace.h
@@ -278,7 +278,7 @@ public:
         ToolTip = Popup | Sheet,
         SplashScreen = ToolTip | Dialog,
         Desktop = 0x00000010 | Window,
-        SubWindow = Desktop | Dialog,
+        SubWindow = 0x00000012,
 
         WindowType_Mask = 0x000000ff,
         MSWindowsFixedSizeDialogHint = 0x00000100,
diff --git a/src/widgets/kernel/qwidget_qpa.cpp b/src/widgets/kernel/qwidget_qpa.cpp
index c2b60d0387..2120e40c57 100644
--- a/src/widgets/kernel/qwidget_qpa.cpp
+++ b/src/widgets/kernel/qwidget_qpa.cpp
@@ -96,6 +96,12 @@ void QWidgetPrivate::create_sys(WId window, bool initializeWindow, bool destroyO
     QWindowSurface *surface = q->windowSurface();
 
     QWindow *win = topData()->window;
+    // topData() ensures the extra is created but does not ensure 'window' is non-null
+    // in case the extra was already valid.
+    if (!win) {
+        createTLSysExtra();
+        win = topData()->window;
+    }
 
     win->setWindowFlags(data.window_flags);
     win->setGeometry(q->geometry());
@@ -250,8 +256,8 @@ void QWidgetPrivate::setParent_sys(QWidget *newparent, Qt::WindowFlags f)
 
 QPoint QWidget::mapToGlobal(const QPoint &pos) const
 {
-    int           x=pos.x(), y=pos.y();
-    const QWidget* w = this;
+    int x = pos.x(), y = pos.y();
+    const QWidget *w = this;
     while (w) {
         x += w->data->crect.x();
         y += w->data->crect.y();
@@ -262,8 +268,8 @@ QPoint QWidget::mapToGlobal(const QPoint &pos) const
 
 QPoint QWidget::mapFromGlobal(const QPoint &pos) const
 {
-    int           x=pos.x(), y=pos.y();
-    const QWidget* w = this;
+    int x = pos.x(), y = pos.y();
+    const QWidget *w = this;
     while (w) {
         x -= w->data->crect.x();
         y -= w->data->crect.y();