I've just noticed that Knot 2.8.4 doesn't compress names in the RDATA of a response. Mostly this is not a problem. However, there is one special query, where this behaviour results in a sub-optimal response. This is the priming query against a root name server (without EDNS). Whereas BIND and NSD both return a priming response containing 15 glue records, Knot only returns 4 glue records, because it has no more space left for the others. This does not break anything, but a resolver has to issue several follow-up queries to obtain the remaining A and AAAA records of the root name servers.