Saintmode troublelist - cannot add object

[Alexandr Bubenchikov]

Hi guys. First of all sorry for my poor english.

I don't know what mailing list is the best for this question, I believe this is correct one :)

I want to put backend to saintmode, depending on response body. I've created topic in varnish forum - https://www.varnish-cache.org/forum/topic/1182, there is my configuration
std.syslog shows, that set beresp.saintmode being called, but varnish still consider server healthy and I can see requests to "sick" server.

I've put some logs into cache_backend.c, in function vbe_Healthy
    if (sp->objcore == NULL) 
    {
        VSL(SLT_Debug, 0, "========= objcore is null, returning 1");
        return (1);
    }
currently URL is not being added to blacklist because sp->objcore pointer is null (line 281 in 3.0.4 release)  I can't see this line in trunk version (as I understood saint mode will be moved to vmods). I can't understand what objcore is, and why is it null.

Is it something wrong in my varnish config, or backend response should have some required fields? I couldn't find any information in varnish documentation.  

Thanks, Alexander.