diff --git a/src/ai/ai.h b/src/ai/ai.h
--- a/src/ai/ai.h
+++ b/src/ai/ai.h
@@ -43,8 +43,8 @@ void AI_PlayerDied(PlayerID player);
 void AI_RunGameLoop();
 void AI_Initialize();
 void AI_Uninitialize();
-int32 AI_DoCommand(TileIndex tile, uint32 p1, uint32 p2, uint32 flags, uint procc);
-int32 AI_DoCommandCc(TileIndex tile, uint32 p1, uint32 p2, uint32 flags, uint procc, CommandCallback* callback);
+CommandCost AI_DoCommand(TileIndex tile, uint32 p1, uint32 p2, uint32 flags, uint procc);
+CommandCost AI_DoCommandCc(TileIndex tile, uint32 p1, uint32 p2, uint32 flags, uint procc, CommandCallback* callback);
 
 /** Is it allowed to start a new AI.
  * This function checks some boundries to see if we should launch a new AI.