diff --git a/library/src/calculate_price.cpp b/library/src/calculate_price.cpp
index 2d34c7b..0041d08 100644
--- a/library/src/calculate_price.cpp
+++ b/library/src/calculate_price.cpp
@@ -43,13 +43,24 @@ int CALCULATE_LIBRARY_API get_minimal_parkingtime(Configuration const *cfg,
                                                   int paymentOptionIndex) {
     int minTime = 0;
 
+    // tariffs are only set if there is a Includes-section in the tariff-file,
+    // which means the code below will be executed only in such a case.
+    if (tariffs.count(permitType) > 0) {
+        Configuration *c = tariffs[permitType].get();
+        if (c && c != cfg) {
+            cfg = c;
+        }
+    }
+
     paymentOptionIndex = getPaymentOptionIndex(*cfg);
     if (paymentOptionIndex == -1) {
         paymentOptionIndex = cfg->getPaymentOptionIndex(permitType);
     }
 
     qCritical() << __func__ << __LINE__ << "paymentOptionIndex" << paymentOptionIndex;
-    qCritical() << __func__ << __LINE__ << "permit" << PermitType(permitType).toString();
+    qCritical() << __func__ << __LINE__ << "permit" << (int)permitType << PermitType(permitType).toString();
+    qCritical() << __func__ << __LINE__ << "min_time" << (int)permitType << cfg->getPaymentOptions(paymentOptionIndex).pop_min_time;
+    qCritical() << __func__ << __LINE__ << "min_price" << (int)permitType << cfg->getPaymentOptions(paymentOptionIndex).pop_min_price;
 
     switch(permitType) {
     case PERMIT_TYPE::SHORT_TERM_PARKING: { // e.g. szeged (customer_281)
@@ -79,6 +90,15 @@ int CALCULATE_LIBRARY_API get_maximal_parkingtime(Configuration const *cfg,
                                                   PERMIT_TYPE permitType,
                                                   int paymentOptionIndex) {
 
+    // tariffs are only set if there is a Includes-section in the tariff-file,
+    // which means the code below will be executed only in such a case.
+    if (tariffs.count(permitType) > 0) {
+        Configuration *c = tariffs[permitType].get();
+        if (c && c != cfg) {
+            cfg = c;
+        }
+    }
+
     paymentOptionIndex = getPaymentOptionIndex(*cfg);
     if (paymentOptionIndex == -1) {
         paymentOptionIndex = cfg->getPaymentOptionIndex(permitType);
@@ -109,6 +129,15 @@ int CALCULATE_LIBRARY_API get_minimal_parkingprice(Configuration *cfg,
                                                    QDateTime const &start) {
     int minPrice = -1;
 
+    // tariffs are only set if there is a Includes-section in the tariff-file,
+    // which means the code below will be executed only in such a case.
+    if (tariffs.count(permitType) > 0) {
+        Configuration *c = tariffs[permitType].get();
+        if (c && c != cfg) {
+            cfg = c;
+        }
+    }
+
     if ((paymentOptionIndex = getPaymentOptionIndex(*cfg, start)) == -1) {
         paymentOptionIndex = cfg->getPaymentOptionIndex(permitType);
     }
@@ -173,6 +202,14 @@ int CALCULATE_LIBRARY_API compute_product_price(Configuration const *cfg,
                                                 QDateTime const &start,
                                                 QDateTime *productStart,
                                                 QDateTime *productEnd) {
+    // tariffs are only set if there is a Includes-section in the tariff-file,
+    // which means the code below will be executed only in such a case.
+    if (tariffs.count(permitType) > 0) {
+        Configuration *c = tariffs[permitType].get();
+        if (c && c != cfg) {
+            cfg = c;
+        }
+    }
 
     switch(permitType) {
     case PERMIT_TYPE::SHORT_TERM_PARKING: { // e.g. szeged (customer_281)
@@ -336,6 +373,16 @@ int CALCULATE_LIBRARY_API get_maximal_parkingprice(Configuration *cfg,
                                                    PERMIT_TYPE permitType,
                                                    int paymentOptionIndex) {
     int maxPrice = -1;
+
+    // tariffs are only set if there is a Includes-section in the tariff-file,
+    // which means the code below will be executed only in such a case.
+    if (tariffs.count(permitType) > 0) {
+        Configuration *c = tariffs[permitType].get();
+        if (c && c != cfg) {
+            cfg = c;
+        }
+    }
+
     static const PaymentMethod paymentMethodId = Utilities::getPaymentMethodId(cfg);
 
     if ((paymentOptionIndex = getPaymentOptionIndex(*cfg)) == -1) {
@@ -724,6 +771,15 @@ CalcState CALCULATE_LIBRARY_API compute_price_for_parking_ticket(
     start = start.toLocalTime().addSecs(start_parking_time * 60);
     QDateTime end(start);
 
+    // tariffs are only set if there is a Includes-section in the tariff-file,
+    // which means the code below will be executed only in such a case.
+    if (tariffs.count(permitType) > 0) {
+        parking_tariff_t *t = tariffs[permitType].get();
+        if (t && t != tariff) {
+            tariff = t;
+        }
+    }
+
     int paymentOptionIndex = getPaymentOptionIndex(*tariff, start);
     if (paymentOptionIndex == -1) {
         paymentOptionIndex = tariff->getPaymentOptionIndex(permitType.get());
@@ -799,6 +855,15 @@ CalcState CALCULATE_LIBRARY_API compute_price_for_parking_ticket(
 
     QDateTime start_parking_time(start_parking_time_);
 
+    // tariffs are only set if there is a Includes-section in the tariff-file,
+    // which means the code below will be executed only in such a case.
+    if (tariffs.count(permitType) > 0) {
+        parking_tariff_t *t = tariffs[permitType].get();
+        if (t && t != tariff) {
+            tariff = t;
+        }
+    }
+
     int paymentOptionIndex = getPaymentOptionIndex(*tariff, start_parking_time);
     if (paymentOptionIndex == -1) {
         paymentOptionIndex = tariff->getPaymentOptionIndex(permitType);
@@ -1077,6 +1142,15 @@ CalcState CALCULATE_LIBRARY_API compute_duration_for_parking_ticket(
         QString &duration,
         PermitType permitType) {
 
+    // tariffs are only set if there is a Includes-section in the tariff-file,
+    // which means the code below will be executed only in such a case.
+    if (tariffs.count(permitType) > 0) {
+        parking_tariff_t *t = tariffs[permitType].get();
+        if (t && t != tariff) {
+            tariff = t;
+        }
+    }
+
     tariff->getPaymentOptions(0).pop_max_price
         = tariff->getPaymentOptions(0).pop_max_price_save;
 
@@ -1135,8 +1209,13 @@ CalcState CALCULATE_LIBRARY_API compute_duration_for_parking_ticket(
         QDateTime &ticketEndTime,
         PermitType permitType)
 {
+    // tariffs are only set if there is a Includes-section in the tariff-file,
+    // which means the code below will be executed only in such a case.
     if (tariffs.count(permitType) > 0) {
-        tariff = tariffs[permitType].get();
+        parking_tariff_t *t = tariffs[permitType].get();
+        if (t && t != tariff) {
+            tariff = t;
+        }
     }
 
     tariff->getPaymentOptions(0).pop_max_price
@@ -1474,8 +1553,17 @@ CalcState CALCULATE_LIBRARY_API compute_duration_for_parking_ticket(
 CalcState CALCULATE_LIBRARY_API compute_duration_for_daily_ticket(parking_tariff_t *tariff,
                                                                   QDateTime const &start_parking_time,
                                                                   QDateTime &ticketEndTime,
-                                                                  PermitType /* PermitType */)
+                                                                  PermitType permitType)
 {
+    // tariffs are only set if there is a Includes-section in the tariff-file,
+    // which means the code below will be executed only in such a case.
+    if (tariffs.count(permitType) > 0) {
+        parking_tariff_t *t = tariffs[permitType].get();
+        if (t && t != tariff) {
+            tariff = t;
+        }
+    }
+
     tariff->getPaymentOptions(0).pop_max_price
         = tariff->getPaymentOptions(0).pop_max_price_save;
 
@@ -1511,6 +1599,15 @@ CalcState CALCULATE_LIBRARY_API compute_price_for_daily_ticket(
                                     PERMIT_TYPE permitType,
                                     struct price_t *price) {// return value
 
+    // tariffs are only set if there is a Includes-section in the tariff-file,
+    // which means the code below will be executed only in such a case.
+    if (tariffs.count(permitType) > 0) {
+        parking_tariff_t *t = tariffs[permitType].get();
+        if (t && t != tariff) {
+            tariff = t;
+        }
+    }
+
     tariff->getPaymentOptions(0).pop_max_price
         = tariff->getPaymentOptions(0).pop_max_price_save;