Unknown setting 'message_format' for output/redis

Hi,

i run logstash on Debian 7/amd64/linux 3.2.0-4 with the folllowing command:
/usr/bin/java -Djava.io.tmpdir=/tmp/ -jar /home/logstash/logstash-monolithic.jar agent -f /home/logstash/etc/conf-enabled --log /var/log/logstash/logstash.log as user logstash.

in /home/logstash/etc/conf-enabled is onle file (i removed the others) which contains this snippet http://cookbook.logstash.net/recipes/central-syslog/logstash-indexer.conf

Trying to reload the running server gives me this error:

{:message=>"SIGHUP received, reloading.", :level=>:warn}
{:message=>"Unknown setting 'message_format' for output/redis", :level=>:error}
{:message=>"Config validation failed.", :level=>:error}
{:message=>"Aborting reload due to bad configuration", :exception=>#<SystemExit: exit>, :level=>:error}