diff --git a/npf.c b/npf.c
--- a/npf.c
+++ b/npf.c
@@ -1,6 +1,7 @@
 #include "stdafx.h"
 #include "openttd.h"
 #include "debug.h"
+#include "functions.h"
 #include "npf.h"
 #include "aystar.h"
 #include "macros.h"