diff --git a/puppet/templates/puppet.conf.erb b/puppet/templates/puppet.conf.erb
index 67fa186..4b9343d 100644
--- a/puppet/templates/puppet.conf.erb
+++ b/puppet/templates/puppet.conf.erb
@@ -38,5 +38,8 @@
     # The default value is '$confdir/localconfig'.
     localconfig = $vardir/localconfig
 
+    # Use yaml for serialization (kerberos keytabs fail with pson)
+    preferred_serialization_format = yaml
+
     # Enable dot graphs of configuration depencies
     graph = true