diff --git a/src/vehicle_func.h b/src/vehicle_func.h
--- a/src/vehicle_func.h
+++ b/src/vehicle_func.h
@@ -11,6 +11,7 @@
 #define VEHICLE_FUNC_H
 
 #include "gfx_type.h"
+#include "date_type.h"
 #include "direction_type.h"
 #include "command_type.h"
 #include "vehicle_type.h"