ADD_ONION command returns "Missing 'Port' argument" when null terminator is present at end

So I naively sent:

"ADD_ONION ED25519-V3:$(base64PrivateKey)\0"

over the control port including the NULL terminator from my C string. Rather than yelling at me for sending non-printable characters (or something similar), the command returned "Missing 'Port' argument"

Seems weird.

EDIT: tor --version -> "Tor version 0.4.3.6"

Edited Aug 19, 2020 by morgan

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