diff --git a/convert/main.c b/convert/main.c
index 95ceec11..fc139e4a 100644
--- a/convert/main.c
+++ b/convert/main.c
@@ -1134,7 +1134,6 @@ static int do_convert(const char *devname, u32 convert_flags, u32 nodesize,
 	int ret;
 	int fd = -1;
 	u32 blocksize;
-	u64 total_bytes;
 	struct btrfs_root *root;
 	struct btrfs_root *image_root;
 	struct btrfs_convert_context cctx;
@@ -1161,7 +1160,6 @@ static int do_convert(const char *devname, u32 convert_flags, u32 nodesize,
 
 	ASSERT(cctx.total_bytes != 0);
 	blocksize = cctx.blocksize;
-	total_bytes = (u64)blocksize * (u64)cctx.block_count;
 	if (blocksize < 4096) {
 		error("block size is too small: %u < 4096", blocksize);
 		goto fail;
@@ -1223,7 +1221,7 @@ static int do_convert(const char *devname, u32 convert_flags, u32 nodesize,
 
 	mkfs_cfg.csum_type = csum_type;
 	mkfs_cfg.label = cctx.label;
-	mkfs_cfg.num_bytes = total_bytes;
+	mkfs_cfg.num_bytes = cctx.total_bytes;
 	mkfs_cfg.nodesize = nodesize;
 	mkfs_cfg.sectorsize = blocksize;
 	mkfs_cfg.stripesize = blocksize;
diff --git a/convert/source-ext2.c b/convert/source-ext2.c
index 9fad4c50..610db16b 100644
--- a/convert/source-ext2.c
+++ b/convert/source-ext2.c
@@ -92,8 +92,8 @@ static int ext2_open_fs(struct btrfs_convert_context *cctx, const char *name)
 
 	cctx->fs_data = ext2_fs;
 	cctx->blocksize = ext2_fs->blocksize;
-	cctx->block_count = ext2_fs->super->s_blocks_count;
-	cctx->total_bytes = (u64)ext2_fs->super->s_blocks_count * ext2_fs->blocksize;
+	cctx->block_count = ext2fs_blocks_count(ext2_fs->super);
+	cctx->total_bytes = cctx->block_count * cctx->blocksize;
 	cctx->label = strndup((char *)ext2_fs->super->s_volume_name, 16);
 	cctx->first_data_block = ext2_fs->super->s_first_data_block;
 	cctx->inodes_count = ext2_fs->super->s_inodes_count;