diff --git a/src/Mod/Fem/Gui/TaskPostBoxes.cpp b/src/Mod/Fem/Gui/TaskPostBoxes.cpp
index 5139b81505..0f379b0548 100644
--- a/src/Mod/Fem/Gui/TaskPostBoxes.cpp
+++ b/src/Mod/Fem/Gui/TaskPostBoxes.cpp
@@ -40,6 +40,7 @@
 # include <sstream>
 
 # include <QApplication>
+# include <QMessageBox>
 #endif
 
 #include "ui_TaskPostDisplay.h"