Adding an action to a build using a Ruby plugin causes the build to fail to load when Jenkins is restarted.

The error looks like this:

SEVERE: Failed Loading job cool
java.lang.ClassCastException: org.jruby.RubyObject cannot be cast to hudson.model.Action
	at hudson.model.Run.onLoad(Run.java:293)
	at hudson.model.RunMap.load(RunMap.java:234)
	at hudson.model.AbstractProject.onLoad(AbstractProject.java:254)
	at hudson.model.Project.onLoad(Project.java:88)
	at hudson.model.Items.load(Items.java:115)
	at jenkins.model.Jenkins$14.run(Jenkins.java:2360)
	at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
	at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
	at jenkins.model.Jenkins$5.runTask(Jenkins.java:800)
	at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:187)
	at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:94)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:680)

The bug was originally mentioned in IRC on April 11th by dragonkh_: http://echelog.com/logs/browse/jenkins/1334095200

Relevant parts of the IRC conversattion:

<cowboyd> dragonkh_: do you get an exception on startup?
<dragonkh_> cowboyd - it happens when I start up jenkins
<dragonkh_> cowboyd - http://pastie.org/3768530
<dragonkh_> cowboyd - thats the exception I get on starting up jenkins - the job fails to load
<dragonkh_> is it in the ruby-runtime somewhere?
<cowboyd> can you send me the xml for the job?
<cowboyd> It's the persistence that is getting confused.
<dragonkh_> cowboyd - isnt this the config? http://pastie.org/3768541
<dragonkh_> cowboyd - check my code here: https://github.com/masterthought/jenkins-cucumber-jvm-reports-plugin
<cowboyd> dragonkh: can I see the xml for the build?
<dragonkh_> cowboyd - http://pastie.org/3768765
<cowboyd> yes, that's it. kohsuke: ^^ any idea why jruby-xstream would be handing the ruby object and not the jruby proxy?

<dragonkh> cowboyd - got any idea where I can have a look ?
<cowboyd> yes, it's in the deserialization code. https://github.com/jenkinsci/jruby-xstream
<dragonkh> is that part of the main jenkins release?
<cowboyd> all ruby plugins depend on it
<dragonkh> or is it part of the ruby-runtime ?
<cowboyd> jenkins.rb/java-runtime depends on it