diff --git a/manifests/master.pp b/manifests/master.pp
index 287677a..32b760f 100644
--- a/manifests/master.pp
+++ b/manifests/master.pp
@@ -1,147 +1,147 @@
 # munin::master - Define a munin master
 #
 # The munin master will install munin, and collect all exported munin
 # node definitions as files into /etc/munin/munin-conf.d/.
 #
 # Parameters:
 #
 # - node_definitions: A hash of node definitions used by
 #   create_resources to make static node definitions.
 #
 # - host_name: A host name for this munin master, matched with
 #   munin::node::mastername for collecting nodes. Defaults to $::fqdn
 #
 # - graph_strategy: 'cgi' (default) or 'cron'
 #   Controls if munin-graph graphs all services ('cron') or if graphing is done
 #   by munin-cgi-graph (which must configured seperatly)
 #
 # - html_strategy: 'cgi' (default) or 'cron'
 #   Controls if munin-html will recreate all html pages every run interval
 #   ('cron') or if html pages are generated by munin-cgi-graph (which must
 #   configured seperatly)
 #
 # - config_root: the root directory of the munin master configuration.
 #   Default: /etc/munin on most platforms.
 #
 # - collect_nodes: 'enabled' (default), 'disabled', 'mine' or
 #   'unclaimed'. 'enabled' makes the munin master collect all exported
 #   node_definitions. 'disabled' disables it. 'mine' makes the munin
 #   master collect nodes matching $munin::master::host_name, while
 #   'unclaimed' makes the munin master collect nodes not tagged with a
 #   host name.
 #
 # - dbdir: Path to the munin dbdir, where munin stores everything
 #
 # - htmldir: Path to where munin will generate HTML documents and
 #   graphs, used if graph_strategy is cron.
 #
 # - rundir: Path to directory munin uses for pid and lock files.
 #
 # - tls: 'enabled' or 'disabled' (default). Controls the use of TLS
 #   globally for master to node communications.
 #
 # - tls_certificate: Path to a file containing a TLS certificate. No
 #   default. Required if tls is enabled.
 #
 # - tls_private_key: Path to a file containing a TLS key. No default.
 #   Required if tls is enabled.
 #
 # - tls_verify_certificate: 'yes' (default) or 'no'.
 #
 # - extra_config: Extra lines of config to put in munin.conf.
 
 class munin::master (
   $node_definitions       = $munin::params::master::node_defintions,
   $graph_strategy         = $munin::params::master::graph_strategy,
   $html_strategy          = $munin::params::master::html_strategy,
   $config_root            = $munin::params::master::config_root,
   $collect_nodes          = $munin::params::master::collect_nodes,
   $dbdir                  = $munin::params::master::dbdir,
   $htmldir                = $munin::params::master::htmldir,
   $logdir                 = $munin::params::master::logdir,
   $rundir                 = $munin::params::master::rundir,
   $tls                    = $munin::params::master::tls,
   $tls_certificate        = $munin::params::master::tls_certificate,
   $tls_private_key        = $munin::params::master::tls_private_key,
   $tls_verify_certificate = $munin::params::master::tls_verify_certificate,
   $host_name              = $munin::params::master::host_name,
   $extra_config           = $munin::params::master::extra_config,
   ) inherits munin::params::master {
 
   if $node_definitions {
     validate_hash($node_definitions)
   }
   if $graph_strategy {
     validate_re($graph_strategy, [ '^cgi$', '^cron$' ])
   }
   if $html_strategy {
     validate_re($html_strategy, [ '^cgi$', '^cron$' ])
   }
   validate_re($collect_nodes, [ '^enabled$', '^disabled$', '^mine$',
                                 '^unclaimed$' ])
   validate_absolute_path($config_root)
 
   validate_re($tls, [ '^enabled$', '^disabled$' ])
 
   if $tls == 'enabled' {
     validate_re($tls_verify_certificate, [ '^yes$', '^no$' ])
     validate_absolute_path($tls_private_key)
     validate_absolute_path($tls_certificate)
   }
 
   if $host_name {
     validate_string($host_name)
-    if ! is_domain_name($host_name) {
+    if ! is_domain_name("${host_name}") {
       fail('host_name should be a valid domain name')
     }
   }
 
   validate_array($extra_config)
 
   # The munin package and configuration
   package { 'munin':
     ensure => latest,
   }
 
   File {
     owner   => 'root',
     group   => 'root',
     mode    => '0644',
     require => Package['munin'],
   }
 
   file { "${config_root}/munin.conf":
     content => template('munin/munin.conf.erb'),
   }
 
   file { "${config_root}/munin-conf.d":
     ensure  => directory,
     recurse => true,
     purge   => true,
     force   => true,
   }
 
   case $collect_nodes {
     'enabled': {
       Munin::Master::Node_definition <<| |>>
     }
     'mine': {
       # Collect nodes explicitly tagged with this master
       Munin::Master::Node_definition <<| tag == "munin::master::${host_name}" |>>
     }
     'unclaimed': {
       # Collect all exported node definitions, except the ones tagged
       # for a specific master
       Munin::Master::Node_definition <<| tag == 'munin::master::' |>>
     }
     'disabled',
     default: {
       # do nothing
     }
   }
 
   # Create static node definitions
   if $node_definitions {
     create_resources(munin::master::node_definition, $node_definitions, {})
   }
 }