According to some embodiments, a method for use in a user equipment (UE) of managing a listen-before-talk (LBT) contention window size comprises performing a first LBT procedure using a first contention window size and priority class for a first uplink transmission in unlicensed spectrum. The first uplink transmission comprises an acknowledged transmission. The method further comprises transmitting a second uplink transmission. The second uplink transmission comprises an un-acknowledged transmission. The method further comprises receiving an acknowledgement for the first uplink transmission, and modifying both the first contention window size and a second contention window based on the received acknowledgement. The method further comprises performing a second LBT procedure using the secondcontention window size and a second priority class for a third uplink transmission in unlicensed spectrum. The third uplink transmission comprises an un-acknowledged transmission.