Probable bug when piped into Hash

[tedmx]

fstream_hash_issue_example.js computes MD5 hash of a file read from filesystem.

Program call and output in cmd.exe, Windows :

F:\...>node fstream_hash_issue_example.js
fs.createReadStream: dd9e30aa94c1074d863846c4ed35b8bd
fstream.Reader: d41d8cd98f00b204e9800998ecf8427e
fstream.Reader: dd9e30aa94c1074d863846c4ed35b8bd

The code:

var crypto = require('crypto'),
    fs = require('fs'),
    fstream = require('fstream'),
    through = require('through2');

function getHasher(tag){

    var md5Hasher = crypto.createHash('md5', { encoding: 'hex' });
    md5Hasher.on('readable', () => {

        var data = md5Hasher.read();
        if (data)
            console.log(
                tag+data
            );
    });

    return md5Hasher;
}   

fs.createReadStream("program.js").pipe(getHasher('fs.createReadStream: '));
fstream.Reader("program.js").pipe(getHasher('fstream.Reader: '));
fstream.Reader("program.js").pipe(through(
    //No-op stream
    function(buf,_,next){
        this.push(buf);
        next();
    }
)).pipe(getHasher('fstream.Reader: '));

Environment: Windows 10 Pro, node v.4.2.4, fstream 1.0.10