const struct scarlett2_device_info *info = private->info;
        const struct scarlett2_ports *ports = info->ports;
        int oval, val, num_mixer_in, mix_num, err = 0;
+       int index = elem->control;
 
        mutex_lock(&private->data_mutex);
 
-       oval = private->mix[elem->control];
+       oval = private->mix[index];
        val = ucontrol->value.integer.value[0];
        num_mixer_in = ports[SCARLETT2_PORT_TYPE_MIX].num[SCARLETT2_PORT_OUT];
-       mix_num = elem->control / num_mixer_in;
+       mix_num = index / num_mixer_in;
 
        if (oval == val)
                goto unlock;
 
-       private->mix[elem->control] = val;
+       private->mix[index] = val;
        err = scarlett2_usb_set_mix(mixer, mix_num);
        if (err == 0)
                err = 1;