diff --git a/ai_build.c b/ai_build.c
--- a/ai_build.c
+++ b/ai_build.c
@@ -1,5 +1,6 @@
 #include "stdafx.h"
 #include "ttd.h"
+#include "map.h"
 #include "command.h"
 #include "ai.h"
 #include "engine.h"