For the sake of overtopping, stability and economy, rubble mound breakwaters have been built with a berm in the seaward slope. Here, a breakwater model with cube armour units in the lower slope and a horizontal berm, and rock in the upper slope was tested experimentally. The purpose of the study was to investigate the stability of berms for two different configurations of the transition of armor units from the lower slope to the berm. Based on the test results, an effective configuration of cube units at the transition has been obtained.