[knot-dns-users] Error with secondaries: IXFR failed to start (not enough memory)

Hi. I have a KNOT master with a small zone (32 records), which is logging an error after the secondary (BIND) tries to update the zone. AFAIK, Bind tries with IXFR first, but my master says: 2016-08-19T16:32:12 error: [manojitos.cl] IXFR, outgoing, 200.1.123.7@29095: failed to start (not enough memory) After that the secondary retries with AXFR, and that works: 2016-08-19T16:32:12 info: [manojitos.cl] AXFR, outgoing, 200.1.123.7@13644: started, serial 2016011013 2016-08-19T16:32:12 info: [manojitos.cl] AXFR, outgoing, 200.1.123.7@13644: finished, 0.00 seconds, 1 messages, 2573 bytes The error is the same the first time I provision the zone in the secondary as in following updates. Is there a bug in the error message, or should I worry for some memory requirement in my server (or service)? I'm with Knot 2.3.0 on a FreeBSD 10.3-release-p7. The secondary is not under my administration, but I was told is Bind with an up-to-date version. Thanks! Hugo