There is provided a method comprising: determining, by a transmitter node, maximum packet duration for a data packet to be transmitted, wherein the data packet comprises a plurality of data units; causing a transmission of the data packet; causing a reception of an acknowledgement frame indicating a failed reception of multiple consecutive data units of the transmitted data packet; determining a transmission duration during which the failed multiple consecutive data units were transmitted; and determining whether or not to adjust the maximum packet duration for upcoming data packet transmissions on the basis of the determined transmission duration.