乘客在 Puppet 3.0.0 升级后为“master”抛出未定义的方法`-@'：String

我的 Puppet master 使用 Passenger 来服务。升级到 Puppet 3.0.0 后出现以下错误：

[ pid=17576 thr=70231398486460 file=utils.rb:176 time=2012-10-01 17:37:12.892 ]: *** PhusionPassenger::Rack::ApplicationSpawner 中的异常 NoMethodError（未定义的方法`-@' 用于“ master":String)（进程 17576，线程 #）：
        来自 config.ru:7
        来自 /usr/lib/ruby/gems/1.8/gems/rack-1.4.1/lib/rack/builder.rb:51:in `instance_eval'
        来自 /usr/lib/ruby/gems/1.8/gems/rack-1.4.1/lib/rack/builder.rb:51:in `initialize'
        来自 config.ru:1:in `new'
        来自 config.ru:1

我的config.ru如下：

# a config.ru, for use with every rack-compatible webserver.
# SSL needs to be handled outside this, though.

# if puppet is not in your RUBYLIB:
# $LOAD_PATH.unshift('/opt/puppet/lib')

$0 = "master"

# if you want debugging:
# ARGV << "--debug"

ARGV << "--rack"

# Rack applications typically don't start as root.  Set --confdir to prevent
# reading configuration from ~/.puppet/puppet.conf
ARGV << "--confdir" << "/etc/puppet"

# NOTE: it's unfortunate that we have to use the "CommandLine" class
#  here to launch the app, but it contains some initialization logic
#  (such as triggering the parsing of the config file) that is very
#  important.  We should do something less nasty here when we've
#  gotten our API and settings initialization logic cleaned up.
#
# Also note that the "$0 = master" line up near the top here is
#  the magic that allows the CommandLine class to know that it's
#  supposed to be running master.
#
# --cprice 2012-05-22

require 'puppet/util/command_line'
# we're usually running inside a Rack::Builder.new {} block,
# therefore we need to call run *here*.
run Puppet::Util::CommandLine.new.execute

知道会发生什么吗？