Example fails on "invalid magic number: 0"

[Raythonic]

rwalk@walkubu:/mnt/data3/git2/RustyNode$ sudo target/debug/rusty_node /dev/sdc
thread 'main' panicked at 'ext4 volume: failed to parse superblock

Caused by:
filesystem uses an unsupported feature: "invalid magic number: 0"', src/main.rs:10:63
note: run with RUST_BACKTRACE=1 environment variable to display a backtrace

`extern crate ext4;

use std::env;
use std::fs;

fn main() {
let r = fs::File::open(env::args().nth(1).expect("one argument")).expect("openable file");
let mut options = ext4::Options::default();
options.checksums = ext4::Checksums::Enabled;
let vol = ext4::SuperBlock::new_with_options(r, &options).expect("ext4 volume");
let root = vol.root().expect("root");
vol.walk(&root, "/", &mut |_, path, _, _| {
println!("{}", path);
Ok(true)
})
.expect("walk");
}`