diff --git a/src/slic3r/GUI/GUI.cpp b/src/slic3r/GUI/GUI.cpp
index 15162855c..616d36ba2 100644
--- a/src/slic3r/GUI/GUI.cpp
+++ b/src/slic3r/GUI/GUI.cpp
@@ -21,6 +21,7 @@
 
 #include "AboutDialog.hpp"
 #include "MsgDialog.hpp"
+#include "format.hpp"
 
 #include "libslic3r/Print.hpp"