vinyl-fs: Passing gulp.src() to gulp.pipe() is erroring

My gulp task:

gulp.task('build', ['sass'], function (done) {
    var child = spawn('./node_modules/.bin/r.js', ['-o', 'app/assets/js/app.build.js'], {
        stdio: 'inherit'
    });

    child.on('close', function () {
        gulp.src('app/assets/build/js/main.js')
            .pipe(gulp.dest('app/assets/build'))
            .pipe(gulp.src('app/assets/build/js', {read: false}))
            .pipe(plugins.clean())
            .on('end', done);
    });
});

My error:

stream.js:94
      throw er; // Unhandled stream error in pipe.
            ^
Error: write after end
    at writeAfterEnd (/Users/callumacrae/Sites/finance-finder/node_modules/gulp/node_modules/vinyl-fs/node_modules/through2/node_modules/readable-stream/lib/_stream_writable.js:145:12)
    at Transform.Writable.write (/Users/callumacrae/Sites/finance-finder/node_modules/gulp/node_modules/vinyl-fs/node_modules/through2/node_modules/readable-stream/lib/_stream_writable.js:193:5)
    at Stream.ondata (stream.js:51:26)
    at Stream.EventEmitter.emit (events.js:95:17)
    at queueData (/Users/callumacrae/Sites/finance-finder/node_modules/gulp/node_modules/vinyl-fs/node_modules/map-stream/index.js:43:21)
    at next (/Users/callumacrae/Sites/finance-finder/node_modules/gulp/node_modules/vinyl-fs/node_modules/map-stream/index.js:71:7)
    at /Users/callumacrae/Sites/finance-finder/node_modules/gulp/node_modules/vinyl-fs/node_modules/map-stream/index.js:85:7
    at done (/Users/callumacrae/Sites/finance-finder/node_modules/gulp/node_modules/vinyl-fs/lib/dest/writeContents/index.js:9:5)
    at /Users/callumacrae/Sites/finance-finder/node_modules/gulp/node_modules/vinyl-fs/node_modules/graceful-fs/graceful-fs.js:102:5
    at Object.oncomplete (evalmachine.<anonymous>:107:15)

~/Sites/finance-finder rc-2*  14s
❯ gulp --version
[17:57:19] CLI version 3.8.0
[17:57:19] Local version 3.8.0