diff --git a/src/widgets/dialogs/qmessagebox.cpp b/src/widgets/dialogs/qmessagebox.cpp
index df17399ca7e..f9d58e4d906 100644
--- a/src/widgets/dialogs/qmessagebox.cpp
+++ b/src/widgets/dialogs/qmessagebox.cpp
@@ -1657,12 +1657,15 @@ void QMessageBox::open(QObject *receiver, const char *member)
 
 void QMessageBoxPrivate::setVisible(bool visible)
 {
-    Q_Q(QMessageBox);
-
     // Last minute setup
-    if (autoAddOkButton)
-        q->addButton(QMessageBox::Ok);
-    detectEscapeButton();
+    if (visible) {
+        Q_Q(QMessageBox);
+        if (autoAddOkButton)
+            q->addButton(QMessageBox::Ok);
+        detectEscapeButton();
+    }
+    // On hide, we may be called from ~QDialog(), so prevent accessing
+    // q_ptr as a QMessageBox!
 
     if (canBeNativeDialog())
         setNativeDialogVisible(visible);
@@ -1670,7 +1673,7 @@ void QMessageBoxPrivate::setVisible(bool visible)
     // Update WA_DontShowOnScreen based on whether the native dialog was shown,
     // so that QDialog::setVisible(visible) below updates the QWidget state correctly,
     // but skips showing the non-native version.
-    q->setAttribute(Qt::WA_DontShowOnScreen, nativeDialogInUse);
+    static_cast<QWidget*>(q_ptr)->setAttribute(Qt::WA_DontShowOnScreen, nativeDialogInUse);
 
     QDialogPrivate::setVisible(visible);
 }