An arrangement is provided for sealing the opening of a rotor housing under a low pressure, through which opening a shaft for a spinning rotor extends, which shaft is supported outside of the rotor housing. This arrangement comprises a sealing disk, which is supported floating relative to the opening and which is pressed against a bearing surface by means of a spring element. The floating sealing disk comprises a through bore hole having a narrow tolerance relative to the shaft. The spring element presses against the effect of the low pressure.