diff --git a/src/Gui/View3DInventor.cpp b/src/Gui/View3DInventor.cpp
index 9e1f84a5a6..5b3ed1d8e6 100644
--- a/src/Gui/View3DInventor.cpp
+++ b/src/Gui/View3DInventor.cpp
@@ -32,6 +32,7 @@
 # include <QDropEvent>
 # include <QDragEnterEvent>
 # include <QFileDialog>
+# include <QMdiSubWindow>
 # include <QMessageBox>
 # include <QPainter>
 # include <QPrinter>