Building a War File with Warbler using nokogiri results in GemNotFound exception

I use savon and therefore need nokogiri in my rails project.

The project must be built to a war file.
So if I create the war file with warbler and then deploy it to my apache
tomcat test Server I find this Error in my Logfile:

SEVERE: ERROR: application error
org.jruby.rack.RackInitializationException: Could not find
nokogiri-1.5.5-java in any of the sources

I found this related issue:

but I still have no Idea how to get my war file runing.

Any Ideas?

Best Regards,