diff --git a/newgrf_engine.c b/newgrf_engine.c
--- a/newgrf_engine.c
+++ b/newgrf_engine.c
@@ -7,6 +7,7 @@
 #include "string.h"
 #include "strings.h"
 #include "engine.h"
+#include "newgrf_callbacks.h"
 #include "newgrf_engine.h"
 #include "sprite.h"
 #include "variables.h"