diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index 19e89e71ee2a5b521bcdfa0743c212c701e5ea63..d6d1f87cda6348414b55d9fe5fe8266a37b07acf 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -485,6 +485,7 @@ static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config)
     struct virtio_blk_config blkcfg;
     uint64_t capacity;
     int cylinders, heads, secs;
+    int blk_size = s->conf->logical_block_size;
 
     bdrv_get_geometry(s->bs, &capacity);
     bdrv_get_geometry_hint(s->bs, &cylinders, &heads, &secs);
@@ -492,14 +493,14 @@ static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config)
     stq_raw(&blkcfg.capacity, capacity);
     stl_raw(&blkcfg.seg_max, 128 - 2);
     stw_raw(&blkcfg.cylinders, cylinders);
+    stl_raw(&blkcfg.blk_size, blk_size);
+    stw_raw(&blkcfg.min_io_size, s->conf->min_io_size / blk_size);
+    stw_raw(&blkcfg.opt_io_size, s->conf->opt_io_size / blk_size);
     blkcfg.heads = heads;
     blkcfg.sectors = secs & ~s->sector_mask;
-    blkcfg.blk_size = s->conf->logical_block_size;
     blkcfg.size_max = 0;
     blkcfg.physical_block_exp = get_physical_block_exp(s->conf);
     blkcfg.alignment_offset = 0;
-    blkcfg.min_io_size = s->conf->min_io_size / blkcfg.blk_size;
-    blkcfg.opt_io_size = s->conf->opt_io_size / blkcfg.blk_size;
     memcpy(config, &blkcfg, sizeof(struct virtio_blk_config));
 }