diff --git a/settings_gui.c b/settings_gui.c
--- a/settings_gui.c
+++ b/settings_gui.c
@@ -1,5 +1,6 @@
 #include "stdafx.h"
 #include "openttd.h"
+#include "functions.h"
 #include "string.h"
 #include "strings.h" // XXX GetCurrentCurrencyRate()
 #include "table/sprites.h"