diff --git a/src/base_station_base.h b/src/base_station_base.h
--- a/src/base_station_base.h
+++ b/src/base_station_base.h
@@ -220,7 +220,7 @@ struct SpecializedStation : public BaseS
 	 */
 	static inline T *GetIfValid(size_t index)
 	{
-		return IsValidID(index) ? Get(index) : NULL;
+		return IsValidID(index) ? Get(index) : nullptr;
 	}
 
 	/**