i2pd-tools: vain successful - keyinfo "bad key file format"

Compiled and running on FreeBSD 12.2

I’m looking for a 7 character vanity address, which usually takes a few hours on my E5-2643v3 processor. But when it finds one and exits, I run keyinfo on the output I get the following error:

./keyinfo keyfile5.dat
bad key file format

I also tried on a windows laptop with the release executable (Ryzen 9 5900HX) , and same thing, 6 character vanity addresses work just fine, but whenever I search for and find a 7 character vanity address I get the same error.