gulp-cucumber and gulp-browserstack do not play nicely together

[abendigo]

This is my gulpfile:

var gulp = require('gulp');

var cucumber = require('gulp-cucumber')
var browserStack = require('gulp-browserstack');

gulp.task('cucumber', function() {
  return gulp.src('features/my_feature.feature')
    .pipe(browserStack.startTunnel({
      key: '<itsasecret>'
    }))
    .pipe(cucumber({}))
    .pipe(browserStack.stopTunnel());
});

When all the scenarios pass, gulp hangs, and never exits.