Puppet 2.7.22 agent/master error

problem.sh

info: Retrieving plugin
err: /File[/var/lib/puppet/lib]: Failed to generate additional resources using 'eval_generate: Could not intern_multiple from yaml: Invalid option ftype for Puppet::FileServing::Metadata
err: /File[/var/lib/puppet/lib]: Could not evaluate: Could not intern from yaml: Invalid option ftype for Puppet::FileServing::Metadata Could not retrieve file metadata for puppet://puppet/plugins: Could
not intern from yaml: Invalid option ftype for Puppet::FileServing::Metadata
info: Loading facts in /var/lib/puppet/lib/facter/fqdn_underscore.rb
info: Loading facts in /var/lib/puppet/lib/facter/root_home.rb
info: Loading facts in /var/lib/puppet/lib/facter/iptables_persistent_version.rb
info: Loading facts in /var/lib/puppet/lib/facter/ip6tables_version.rb
info: Loading facts in /var/lib/puppet/lib/facter/iptables_version.rb
info: Loading facts in /var/lib/puppet/lib/facter/facter_dot_d.rb
info: Loading facts in /var/lib/puppet/lib/facter/pe_version.rb
info: Loading facts in /var/lib/puppet/lib/facter/dhcp_enabled.rb
info: Loading facts in /var/lib/puppet/lib/facter/concat_basedir.rb
info: Loading facts in /var/lib/puppet/lib/facter/puppet_vardir.rb
info: Loading facts in /var/lib/puppet/lib/facter/server_id.rb
info: Loading facts in /var/lib/puppet/lib/facter/memtotalmb.rb
err: Could not retrieve catalog from remote server: Could not intern from yaml: Could not convert from pson: Could not find relationship source {"catalog"=> ...

solution.diff

--- /etc/puppet/puppet.conf     2013-06-24 20:53:28.694391061 +0000
+++ /tmp/puppet-file20130624-4226-1p3xklz       2013-06-24 21:00:02.484185256 +0000
@@ -1,5 +1,5 @@
 [main]
-preferred_serialization_format = yaml