diff --git a/library/include/mobilisis/calculate_price.h b/library/include/mobilisis/calculate_price.h
index 66638f5..ab09de4 100644
--- a/library/include/mobilisis/calculate_price.h
+++ b/library/include/mobilisis/calculate_price.h
@@ -109,6 +109,8 @@ CalcState CALCULATE_LIBRARY_API init_tariff(parking_tariff_t **tariff,
 void CALCULATE_LIBRARY_API free_tariff(parking_tariff_t *tariff);
 int CALCULATE_LIBRARY_API get_zone_nr(int zone = -1);
 
+int CALCULATE_LIBRARY_API compute_next_timestep(parking_tariff_t *tariff, int currentTimeMinutes, int UpDown);
+
 CalcState CALCULATE_LIBRARY_API compute_price_for_parking_ticket(       // deprecated
                                             parking_tariff_t *tariff,
                                             time_t start_parking_time,