Casperjs无法执行演示

Question

我的casperjs无法执行example.js，

phantomjs 2.1.1 capserjs 1.1.3

example.js

var casper = require('casper').create();

casper.start('http://casperjs.org/', function() {
    this.echo(this.getTitle());
});

casper.thenOpen('http://phantomjs.org', function() {
    this.echo(this.getTitle());
});

casper.run();

当我执行casperjs example.js时，它会告诉我这个;

ReferenceError: Can't find variable: process
phantomjs://platform/path.js:26