diff --git a/src/plugins/qmldesigner/designercore/filemanager/qmlwarningdialog.h b/src/plugins/qmldesigner/designercore/filemanager/qmlwarningdialog.h
index 158ad72cbf4..61cbaa2c7b0 100644
--- a/src/plugins/qmldesigner/designercore/filemanager/qmlwarningdialog.h
+++ b/src/plugins/qmldesigner/designercore/filemanager/qmlwarningdialog.h
@@ -3,9 +3,11 @@
 
 #include <QDialog>
 
+QT_BEGIN_NAMESPACE
 namespace Ui {
     class QmlWarningDialog;
 }
+QT_END_NAMESPACE
 
 namespace QmlDesigner {