Error: "iv must be 16 bytes"

[wolverinets]

I get the following error when trying to use this plugin with fluentd:

2020-04-30 07:42:32 -0500 [warn]: #0 dump an error event: error_class=ArgumentError error="iv must be 16 bytes" location="C:/opt/td-agent/embedded/lib/ruby/gems/2.4.0/gems/encryptor-3.0.0/lib/encryptor.rb:79:in `iv='" tag="tcp.0" time=2020-04-30 07:42:31.049673700 -0500 record={"log"=>"plain_text"}

Fluentd configuration of this plugin:

@type encryption
passphrase uniquepasswords1
algorithm 'aes-256-cbc'
field 'log'
@log_level trace

I tried to use different passphrase length, but no luck.