[knot-dns-users] key file format for nsupdate

Hi, I am trying to use nsupdate from knot 1.6.1. I have generated key files using dnssec-keygen from BIND 9.9.5. i.e. dnssec-keygen -a HMAC-MD5 -b 256 -n HOST -C host.example.com Whenever I try to use the files with nsupdate -k <file> though I get: ; Error: failed to read key file: public key file is invalid I have also tried without the “-C” to dnssec-keygen. Are there different flags I need? Or does someone have an example of the file format required? Thanks, Andrew