diff --git a/src/ai/trolly/trolly.h b/src/ai/trolly/trolly.h
--- a/src/ai/trolly/trolly.h
+++ b/src/ai/trolly/trolly.h
@@ -10,6 +10,7 @@
 #include "../../vehicle_type.h"
 #include "../../date_type.h"
 #include "../../engine_type.h"
+#include "../../direction_type.h"
 
 /*
  * These defines can be altered to change the behavoir of the AI