Tracking down a LoadError

I’m having a tough time debugging an exception in my local setup:

org.jruby.exceptions.RaiseException: (LoadError) load error:
jruby/rack/rack_ext – java.lang.invoke.WrongMethodTypeException:
MethodHandle(ThreadContext)IRubyObject should be of type
(ThreadContext)IRubyObject

We are using warbler to generate a war file for our rack application.
The
generated file works flawlessly when run with “java -jar thefiile.war”
or
when deployed in Jetty.

But we also need to programatically start a jetty server from our
integration tests; we are using JRuby for that as well. The script to
launch the war file is quite simple:
Exception when bootstrapping jetty with jruby. · GitHub .

When we run the script the exception above is raised, the stacktrace can
be
found on the same gist.

Can anyone point me in the right direction to figure out what’s going
on?