RabbitMQ output + Compress spooler: “wrong number of arguments”

[ceeeekay]

I'm trying to use the compress spooler codec on a previously-working RMQ output, but encoding is failing with Error encoding event {:exception=>#<ArgumentError: wrong number of arguments (1 for 2)> ...

I've stripped my config down to basic input/output and can reproduce it with the following:

input {
generator {
count => 10
message => "test"
}
}

output {

rabbitmq {
codec => compress_spooler {
spool_size => 10
}
exchange => "from-ingress"
exchange_type => "direct"
host => "dev-queue1"
key => "filter-routing-key"
ssl => "true"
port => "5671"
user => "logstash_user"
password => "[not_telling]"
durable => "true"
persistent => "true"
}
}

It seems to be an interaction between rabbitmq and compress_spooler, as other outputs I've tried (file, stdout, tcp) don't throw this error.

Ubuntu 14.04.3
Logstash 2.1.0-1
logstash-output-rabbitmq 3.0.6
logstash-codec-compress_spooler 2.0.2
Openjdk 7u79-2.5.6-0ubuntu1.14.04.1