diff --git a/src/widgets/dialogs/qfontdialog.cpp b/src/widgets/dialogs/qfontdialog.cpp
index ee918992df5..24b91a873dd 100644
--- a/src/widgets/dialogs/qfontdialog.cpp
+++ b/src/widgets/dialogs/qfontdialog.cpp
@@ -956,7 +956,9 @@ void QFontDialog::setVisible(bool visible)
 */
 void QFontDialogPrivate::setVisible(bool visible)
 {
-    Q_Q(QFontDialog);
+    // Don't use Q_Q here! This function is called from ~QDialog,
+    // so Q_Q calling q_func() invokes undefined behavior (invalid cast in q_func()).
+    const auto q = static_cast<QDialog *>(q_ptr);
 
     if (canBeNativeDialog())
         setNativeDialogVisible(visible);