diff --git a/library/include/mobilisis/calculator_functions.h b/library/include/mobilisis/calculator_functions.h
index 8b13d4e..c156f8d 100644
--- a/library/include/mobilisis/calculator_functions.h
+++ b/library/include/mobilisis/calculator_functions.h
@@ -56,7 +56,7 @@ public:
     /// <param name="end_datetime">Date/time of park end to be conducted in ISO8601 format (e.g. 2022-12-25T08:00:00Z) </param>
 	/// <param name="durationMin">Duration of parking in minutes</param>
 	/// <returns>Returns cost (data type: double)</returns>
-    double GetCostFromDuration(Configuration* cfg, uint8_t vehicle_type, const QDateTime start_datetime, QDateTime & end_datetime, int durationMin, bool nextDay = false, bool prepaid = false);
+    double GetCostFromDuration(Configuration* cfg, uint8_t vehicle_type, QDateTime &start_datetime, QDateTime & end_datetime, int durationMin, bool nextDay = false, bool prepaid = false);
 
     // Daily ticket
     QDateTime GetDailyTicketDuration(Configuration* cfg, const QDateTime start_datetime, uint8_t payment_option, bool carry_over);