diff --git a/src/slic3r/GUI/BackgroundSlicingProcess.cpp b/src/slic3r/GUI/BackgroundSlicingProcess.cpp
index 482900c50..816365d90 100644
--- a/src/slic3r/GUI/BackgroundSlicingProcess.cpp
+++ b/src/slic3r/GUI/BackgroundSlicingProcess.cpp
@@ -2,6 +2,7 @@
 #include "GUI_App.hpp"
 #include "GUI.hpp"
 #include "MainFrame.hpp"
+#include "format.hpp"
 
 #include <wx/app.h>
 #include <wx/panel.h>