library version conflict only in hpi:run and junit

[Max Spring]

The plugin I work on uses a library which in turn depends on xalan:xalan:2.7.1.
When running as junit or through hpi:run, my plugin gets to see 
xalan:xalan:2.6.0 and barfs.

The dependency chain (with hpi:run) is

  org.kohsuke.stapler:maven-stapler-plugin:jar:1.16:compile
     jaxen:jaxen:jar:1.1.1:compile
        xom:xom:jar:1.0:compile
           xalan:xalan:jar:2.6.0:compile

Strangely it works in regular execution.

Is there a way that my plugin can see xalan:2.7.1 even when running as hpi:run 
or junit?

I run again Jenkins 1.455.

Thanks!
-Max