Log4j2 input

I'm trying to get log4j2 logging enabled in logstash. I upgraded to logstash-all-plugins-2.4.0-1.noarch. The logstash plugins github page (https://github.com/logstash-plugins?utf8=✓&query=log4) shows logstash-input-log4j2. When I run a configtest: Couldn't find any input plugin named 'log4j2'. I tried '/opt/logstash/bin/logstash-plugin install logstash-input-log4j2' but get a lot of errors: ERROR: Installation Aborted, message: Bundler could not find compatible versions for gem "logstash-core".

Any help is appreciated.