diff --git a/src/slic3r/GUI/AboutDialog.cpp b/src/slic3r/GUI/AboutDialog.cpp
index 884b0ab54..4ded4ec92 100644
--- a/src/slic3r/GUI/AboutDialog.cpp
+++ b/src/slic3r/GUI/AboutDialog.cpp
@@ -5,6 +5,7 @@
 #include "GUI.hpp"
 #include "GUI_App.hpp"
 #include "MainFrame.hpp"
+#include "format.hpp"
 
 namespace Slic3r { 
 namespace GUI {