puppetserver - check_run class not found

[dmcnaught]

When I call puppet-slack like this for my puppetserver instances:
class { 'slack':
is_puppetmaster => false,
}

I get this error on the agent run:
[root@ip-172-31-19-14 puppet]# puppet agent -t
Info: Retrieving pluginfacts
Info: Retrieving plugin
Info: Loading facts
Error: Could not retrieve catalog from remote server: Error 400 on SERVER: Could not find class check_run for i-58b2bba2.puppetserver-ha.tools.developnet.io on node i-58b2bba2.puppetserver-ha.tools.developnet.io
Warning: Not using cache on failed catalog
Error: Could not retrieve catalog; skipping run