@blabno Actually, this is only done for proxy types.  See here:

https://github.com/arquillian/arquillian-extension-rest/blob/master/rest-client/impl/impl-3x/src/main/java/org/jboss/arquillian/extension/rest/client/RestEnricher.java#L96

and:

https://github.com/arquillian/arquillian-extension-rest/blob/master/rest-client/impl/impl-2x/src/main/java/org/jboss/arquillian/extension/rest/client/RestEnricher.java#L93

JAX-RS 2.0 has no support for proxy types.  See here for clarification, indicating that proxy support is rest easy specific: http://docs.jboss.org/resteasy/docs/3.0-beta-3/userguide/html/RESTEasy_Client_Framework.html#d4e2049