diff --git a/library/src/calculate_price.cpp b/library/src/calculate_price.cpp
index d0ffdec..756a7b5 100644
--- a/library/src/calculate_price.cpp
+++ b/library/src/calculate_price.cpp
@@ -893,7 +893,7 @@ CalcState CALCULATE_LIBRARY_API compute_price_for_parking_ticket(
 
                 // handle carry over
                 int minutesUntilCarryOver = effectiveStartTime.time().secsTo(carryOverStart) / 60;
-                if (netto_parking_time > minutesUntilCarryOver) {
+                if ((minutesUntilCarryOver > 0) && (netto_parking_time > minutesUntilCarryOver)) {
                     int const rest = netto_parking_time - minutesUntilCarryOver;
                     QDateTime s(effectiveStartTime);
                     s = s.addSecs(minutesUntilCarryOver * 60);