diff --git a/src/widgets/dialogs/qerrormessage.cpp b/src/widgets/dialogs/qerrormessage.cpp
index f1adb6aa819..6dda2cc09d8 100644
--- a/src/widgets/dialogs/qerrormessage.cpp
+++ b/src/widgets/dialogs/qerrormessage.cpp
@@ -407,7 +407,9 @@ void QErrorMessage::showMessage(const QString &message, const QString &type)
 
 void QErrorMessagePrivate::setVisible(bool visible)
 {
-    Q_Q(QErrorMessage);
+    // 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);