"Error: write after end" when using babelify with gulp

[Problematic]

In my gulpfile, I have a preprocessing task like so:

var gulp = require('gulp');
var transform = require('vinyl-transform');
var browserify = require('browserify');
gulp.task('preprocess:js', function () {
    return gulp.src(['./src/js/index.js'])
        .pipe(transform(function (filename) {
            return browserify()
                .transform(require('babelify'))
                .require(filename, { entry: true })
                .bundle();
        }))
        .pipe(gulp.dest('./dist/js'));
});

Running the task, I get the following stack trace:

Error: write after end
    at writeAfterEnd (/Users/problematic/dev/node_modules/browserify/node_modules/readable-stream/lib/_stream_writable.js:161:12)
    at Labeled.Writable.write (/Users/problematic/dev/node_modules/browserify/node_modules/readable-stream/lib/_stream_writable.js:208:5)
    at write (_stream_readable.js:602:24)
    at flow (_stream_readable.js:611:7)
    at _stream_readable.js:579:7
    at process._tickCallback (node.js:442:13)

This error disappears if I comment out the transform(require('babelify') line of the task.

[sebmck]

Looks like it's due to vinyl-transform. Quick search shows that it's an issue a lot of people run into when using it, browserify/browserify#1044. The suggestion here might work.

[Problematic]

That did the trick; thanks much!