diff --git a/src/slic3r/GUI/Downloader.cpp b/src/slic3r/GUI/Downloader.cpp
index ff66b85c5..4ec4e04eb 100644
--- a/src/slic3r/GUI/Downloader.cpp
+++ b/src/slic3r/GUI/Downloader.cpp
@@ -1,6 +1,7 @@
 #include "Downloader.hpp"
 #include "GUI_App.hpp"
 #include "NotificationManager.hpp"
+#include "format.hpp"
 
 #include <boost/algorithm/string.hpp>
 #include <boost/log/trivial.hpp>