diff --git a/src/ai/ai.hpp b/src/ai/ai.hpp
--- a/src/ai/ai.hpp
+++ b/src/ai/ai.hpp
@@ -8,6 +8,7 @@
 #include "api/ai_event_types.hpp"
 #include "../date_type.h"
 #include "../core/string_compare_type.hpp"
+#include <map>
 
 typedef std::map<const char *, class AIInfo *, StringCompare> AIInfoList;
 
diff --git a/src/ai/ai_core.cpp b/src/ai/ai_core.cpp
--- a/src/ai/ai_core.cpp
+++ b/src/ai/ai_core.cpp
@@ -15,6 +15,7 @@
 #include "ai_scanner.hpp"
 #include "ai_instance.hpp"
 #include "ai_config.hpp"
+#include "api/ai_error.hpp"
 
 /* static */ uint AI::frame_counter = 0;
 /* static */ AIScanner *AI::ai_scanner = NULL;
diff --git a/src/ai/api/ai_event_types.cpp b/src/ai/api/ai_event_types.cpp
--- a/src/ai/api/ai_event_types.cpp
+++ b/src/ai/api/ai_event_types.cpp
@@ -3,6 +3,7 @@
 /** @file ai_event_types.cpp Implementation of all EventTypes. */
 
 #include "ai_event_types.hpp"
+#include "ai_vehicle.hpp"
 #include "../../command_type.h"
 #include "../../strings_func.h"
 #include "../../settings_type.h"
@@ -69,7 +70,7 @@ Money AIEventEnginePreview::GetRunningCo
 	return ::GetEngine(engine)->GetRunningCost();
 }
 
-AIVehicle::VehicleType AIEventEnginePreview::GetVehicleType()
+int32 AIEventEnginePreview::GetVehicleType()
 {
 	switch (::GetEngine(engine)->type) {
 		case VEH_ROAD:     return AIVehicle::VT_ROAD;
diff --git a/src/ai/api/ai_event_types.hpp b/src/ai/api/ai_event_types.hpp
--- a/src/ai/api/ai_event_types.hpp
+++ b/src/ai/api/ai_event_types.hpp
@@ -7,10 +7,7 @@
 
 #include "ai_object.hpp"
 #include "ai_event.hpp"
-#include "ai_town.hpp"
-#include "ai_industry.hpp"
-#include "ai_engine.hpp"
-#include "ai_subsidy.hpp"
+#include "ai_company.hpp"
 
 /**
  * Event Vehicle Crash, indicating a vehicle of yours is crashed.
@@ -268,11 +265,15 @@ public:
 	 */
 	Money GetRunningCost();
 
+#ifdef DOXYGEN_SKIP
 	/**
 	 * Get the type of the offered engine.
 	 * @return The type the engine has.
 	 */
 	AIVehicle::VehicleType GetVehicleType();
+#else
+	int32 GetVehicleType();
+#endif
 
 	/**
 	 * Accept the engine preview.
diff --git a/src/ai/api/ai_object.cpp b/src/ai/api/ai_object.cpp
--- a/src/ai/api/ai_object.cpp
+++ b/src/ai/api/ai_object.cpp
@@ -7,6 +7,7 @@
 #include "../ai.hpp"
 #include "../ai_storage.hpp"
 #include "../ai_instance.hpp"
+#include "ai_error.hpp"
 
 static AIStorage *GetStorage()
 {