diff --git a/src/widgets/widgets/qdialogbuttonbox.cpp b/src/widgets/widgets/qdialogbuttonbox.cpp
index 0ecb97bff7b..545e8bb6dab 100644
--- a/src/widgets/widgets/qdialogbuttonbox.cpp
+++ b/src/widgets/widgets/qdialogbuttonbox.cpp
@@ -294,7 +294,7 @@ void QDialogButtonBoxPrivate::layoutButtons()
         for (QWidget *here : layoutWidgets) {
             QWidget::setTabOrder(prev, here);
             prev = here;
-            if (auto *pushButton = qobject_cast<QPushButton *>(prev); pushButton->isDefault())
+            if (auto *pushButton = qobject_cast<QPushButton *>(prev); pushButton && pushButton->isDefault())
                 q->setFocusProxy(pushButton);
         }
     }