Hi, I'm in the process of doing a migration but I am having some problems and I'm not sure how to approach this. I debugged quite far into the Resteasy JAX-RS integration and also looked at past commits to ServerResponseWriter which is AFAICS the source of the problem. I identified the following two commits related to https://issues.redhat.com/browse/RESTEASY-1227 which might be the reason for my issue: * https://github.com/resteasy/Resteasy/commit/992f605197c52030e88a21145e6ec... * https://github.com/resteasy/Resteasy/commit/fb33d3c1bac91bdb1d686008bb679... The problem I have, is that when a HEAD request is made, which doesn't have an Accept header, Resteasy can't figure out how to encode the result object from my resource method. Previously, Resteasy tried to find a MessageBodyWriter, which it now does not anymore, as it instead throws a NotAcceptableException. As per the comment in the code, this seems to be due to JAX-RS 2.0 section 3.8.6. It seems that the MessageBodyWriter resolving only occurs when there is an Accept header, which is ok if section 3.8.4 were properly respected. It states that "If A = {}, set A {'*/*'}", which AFAICS is exactly what is missing here. If '*/*' were added to A(note that "chosen" is set to that value in the code), the MessageBodyWriter resolving would AFAIK work correctly again for my case. Is this a regression or did I misread the specification? Regards, Christian