if (out->type & VIRTIO_BLK_T_SCSI_CMD) {
                fprintf(stderr, "Scsi commands unsupported\n");
                in->status = VIRTIO_BLK_S_UNSUPP;
-               wlen = sizeof(in);
+               wlen = sizeof(*in);
        } else if (out->type & VIRTIO_BLK_T_OUT) {
                /* Write */
 
                        /* Die, bad Guest, die. */
                        errx(1, "Write past end %llu+%u", off, ret);
                }
-               wlen = sizeof(in);
+               wlen = sizeof(*in);
                in->status = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR);
        } else {
                /* Read */
                ret = readv(vblk->fd, iov+1, in_num-1);
                verbose("READ from sector %llu: %i\n", out->sector, ret);
                if (ret >= 0) {
-                       wlen = sizeof(in) + ret;
+                       wlen = sizeof(*in) + ret;
                        in->status = VIRTIO_BLK_S_OK;
                } else {
-                       wlen = sizeof(in);
+                       wlen = sizeof(*in);
                        in->status = VIRTIO_BLK_S_IOERR;
                }
        }