diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index d6c7aa6f66513d64976935c25818782c723534ef..9285c18cea07fb957e88dbbba05f0b823559631e 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -91,7 +91,7 @@ int scsi_read_data(SCSIDevice *s, uint8_t *data, uint32_t len)
     }
 
     if (len && s->sector_count) {
-        bdrv_read(s->bdrv, s->sector, s->buf, 512);
+        bdrv_read(s->bdrv, s->sector, s->buf, 1);
         s->sector++;
         s->sector_count--;
         s->buf_pos = 0;