diff --git a/library/src/calculator_functions.cpp b/library/src/calculator_functions.cpp
index 57e518f..7e8e3f3 100644
--- a/library/src/calculator_functions.cpp
+++ b/library/src/calculator_functions.cpp
@@ -341,6 +341,15 @@ std::string Calculator::GetDurationFromCost(Configuration* cfg,
///
double Calculator::GetCostFromDuration(Configuration* cfg, uint8_t payment_option, const QDateTime start_datetime, QDateTime & end_datetime, double durationMin, bool nextDay, bool prepaid)
{
+ if (cfg->project.project == "Schoenau" || cfg->project.project == "schoenau") {
+ static QList const timeSteps = GetTimeSteps(cfg, payment_option);
+ if (!timeSteps.contains(durationMin)) {
+ return 0.0f; // error: timestep not valid
+ }
+
+ return GetPriceForTimeStep(cfg, payment_option, durationMin);
+ }
+
// Get input date
QDateTime inputDate = start_datetime;