diff --git a/block.c b/block.c
index 39724c17d3..8385b4fe4f 100644
--- a/block.c
+++ b/block.c
@@ -522,7 +522,7 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
             bdrv_delete(bs1);
             return ret;
         }
-        total_size = bdrv_getlength(bs1) >> BDRV_SECTOR_BITS;
+        total_size = bdrv_getlength(bs1) & BDRV_SECTOR_MASK;
 
         if (bs1->drv && bs1->drv->protocol_name)
             is_protocol = 1;
@@ -541,7 +541,7 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
         bdrv_qcow2 = bdrv_find_format("qcow2");
         options = parse_option_parameters("", bdrv_qcow2->create_options, NULL);
 
-        set_option_parameter_int(options, BLOCK_OPT_SIZE, total_size * 512);
+        set_option_parameter_int(options, BLOCK_OPT_SIZE, total_size);
         set_option_parameter(options, BLOCK_OPT_BACKING_FILE, backing_filename);
         if (drv) {
             set_option_parameter(options, BLOCK_OPT_BACKING_FMT,