diff --git a/ai/trolly/trolly.c b/ai/trolly/trolly.c
--- a/ai/trolly/trolly.c
+++ b/ai/trolly/trolly.c
@@ -34,6 +34,7 @@
 #include "../../engine.h"
 #include "../../gui.h"
 #include "../../depot.h"
+#include "../../vehicle.h"
 #include "../ai.h"
 
 // This function is called after StartUp. It is the init of an AI
diff --git a/newgrf.c b/newgrf.c
--- a/newgrf.c
+++ b/newgrf.c
@@ -19,6 +19,7 @@
 #include "bridge.h"
 #include "economy.h"
 #include "newgrf_engine.h"
+#include "vehicle.h"
 
 /* TTDPatch extended GRF format codec
  * (c) Petr Baudis 2004 (GPL'd)
diff --git a/settings_gui.c b/settings_gui.c
--- a/settings_gui.c
+++ b/settings_gui.c
@@ -19,6 +19,7 @@
 #include "town.h"
 #include "variables.h"
 #include "settings.h"
+#include "vehicle.h"
 
 static uint32 _difficulty_click_a;
 static uint32 _difficulty_click_b;