diff --git a/src/Gui/View3DInventor.h b/src/Gui/View3DInventor.h
index 882265183a..e02d49a54b 100644
--- a/src/Gui/View3DInventor.h
+++ b/src/Gui/View3DInventor.h
@@ -24,6 +24,7 @@
 #define GUI_VIEW3DINVENTOR_H
 
 #include <memory>
+#include <optional>
 #include <QImage>
 #include <QtOpenGL.h>