diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index b750bd8..a16ac75 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -730,6 +730,7 @@
     BlockConf *conf = &s->conf.conf;
     struct virtio_blk_config blkcfg;
     uint64_t capacity;
+    int64_t length;
     int blk_size = conf->logical_block_size;
 
     blk_get_geometry(s->blk, &capacity);
@@ -752,7 +753,8 @@
      * divided by 512 - instead it is the amount of blk_size blocks
      * per track (cylinder).
      */
-    if (blk_getlength(s->blk) /  conf->heads / conf->secs % blk_size) {
+    length = blk_getlength(s->blk);
+    if (length > 0 && length / conf->heads / conf->secs % blk_size) {
         blkcfg.geometry.sectors = conf->secs & ~s->sector_mask;
     } else {
         blkcfg.geometry.sectors = conf->secs;