diff --git a/src/vehicle_func.h b/src/vehicle_func.h
--- a/src/vehicle_func.h
+++ b/src/vehicle_func.h
@@ -25,7 +25,7 @@
 #define IS_CUSTOM_FIRSTHEAD_SPRITE(x) (x == 0xFD)
 #define IS_CUSTOM_SECONDHEAD_SPRITE(x) (x == 0xFE)
 
-static const int VEHICLE_PROFIT_MIN_AGE = DAYS_IN_YEAR * 2; ///< Only vehicles older than this have a meaningful profit.
+static const int VEHICLE_PROFIT_MIN_AGE = CalendarTime::DAYS_IN_YEAR * 2; ///< Only vehicles older than this have a meaningful profit.
 static const Money VEHICLE_PROFIT_THRESHOLD = 10000;        ///< Threshold for a vehicle to be considered making good profit.
 
 /**