I would not expect it to build against 4.2.2 at all, the AS internals have changed substantially. As for 5.0.0.GA, it may predate some shuffling around of AS libraries which will confuse the build script, or it may (less likely) be a problem with cygwin paths not being handled properly. Try AS 5.1.0.Beta1 or build the AS source from branch 5.x maybe? Failing that I'll have to install cygwin into a windows vm and try to recreate the issue. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4223479#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...