When an avatar is requested with a malformed `default` option with no value on a non-existing user the 'mm.png' file is returned. Example: ``` curl -i https://avatars.linux-kernel.at/avatar/nobodyasdasdasdasdashdakhdkjhkaa?d= ``` While not technically against the API this is not the behaviour of both Libravatar 0.1 and Gravatar, where the default 'nobody.png' file is used instead. This is mentioned briefly, although I think not very clearly, in the documentation: > d or default parameter defaults to the Libravatar logo Issue found with my tests script `ivatar.t`.