diff --git a/ship_gui.c b/ship_gui.c
--- a/ship_gui.c
+++ b/ship_gui.c
@@ -20,6 +20,7 @@
 #include "depot.h"
 #include "vehicle_gui.h"
 #include "newgrf_engine.h"
+#include "date.h"
 
 /**
  * Draw the purchase info details of a ship at a given location.