class gerrit {

        class common {
                include standard,
                        gerrit::jetty,
                        gerrit::gitweb,
                        gerrit::crons,
                        role::ldap::config::labs
        }

        define instance(
                $no_apache=false,
                $apache_ssl=false,
                $ircbot=false,
                $slave=false,
                $ssh_port="29418",
                $db_host="",
                $db_name="reviewdb",
                $db_user="gerrit"
        ) {
                # Main config
                $sshport = $ssh_port
                $host = $name
                $dbhost = $db_host
                $dbname = $db_name
                $dbuser = $db_user



<snip -- safe to presume all brackets are properly closed>

class gerrit::jetty ($instance) {
        system_role { "gerrit::jetty": description => "Wikimedia gerrit (git) server" }

        include gerrit::account,
                gerrit::crons,
                gerrit::gerrit_config,
                generic::packages::git-core

        package { [ "openjdk-6-jre", "git-svn" ]:
                ensure => latest;
        }


<snip -- likewise >

=====================================

Now, another file has this in it:

class role::gerrit {

        system_role { "role::gerrit": description => "Gerrit installation" }

        class labs {
                system_role { "role::gerrit::production": description => "Gerrit in labs!" }

                gerrit::instance { "gerrit-dev.wmflabs.org":
                        ircbot => false,
                        db_host => "gerrit-db"
                }

                gerrit::jetty { "labsjetty":
                        instance => gerrit::instance["gerrit-dev.wmflabs.org"]
                }
        }

======================================

Puppet returns the following failure:

err: Could not retrieve catalog from remote server: Error 400 on SERVER: Puppet::Parser::AST::Resource failed with error ArgumentError: Invalid resource type gerrit::jetty at /etc/puppet/manifests/role/gerrit.pp:17 on node i-000003c8.pmtpa.wmflabs


My question:  Why is gerrit::jetty invalid when gerrit::instance, immediately above, is not?