diff --git a/REFERENCE.md b/REFERENCE.md
index 0a522e5..4db1767 100644
--- a/REFERENCE.md
+++ b/REFERENCE.md
@@ -597,7 +597,6 @@ The following parameters are available in the `icinga::server` class:
 * [`zone`](#-icinga--server--zone)
 * [`colocation_endpoints`](#-icinga--server--colocation_endpoints)
 * [`workers`](#-icinga--server--workers)
-* [`extra_zones`](#-icinga--server--extra_zones)
 * [`global_zones`](#-icinga--server--global_zones)
 * [`ca_server`](#-icinga--server--ca_server)
 * [`ticket_salt`](#-icinga--server--ticket_salt)
@@ -650,10 +649,6 @@ All worker zones with key 'endpoints' for endpoint objects.
 
 Default value: `{}`
 
-##### <a name="-icinga--server--extra_zones"></a>`extra_zones`
-
-Additonal zones that are not limited to the 'parent_zone' as parent.
-
 ##### <a name="-icinga--server--global_zones"></a>`global_zones`
 
 Data type: `Array[String]`
diff --git a/manifests/server.pp b/manifests/server.pp
index 7c4d414..dd85a7e 100644
--- a/manifests/server.pp
+++ b/manifests/server.pp
@@ -17,9 +17,6 @@
 # @param workers
 #   All worker zones with key 'endpoints' for endpoint objects.
 #
-# @param extra_zones
-#   Additonal zones that are not limited to the 'parent_zone' as parent.
-#
 # @param global_zones
 #   List of global zones to configure.
 #
@@ -80,7 +77,7 @@
   }
 
   # inject parent zone if no parent exists
-  $_workers = $workers.reduce( {} ) |$memo, $worker| { $memo + { $worker[0] => { parent => $zone } + $worker[1] } }
+  $_workers = $workers.reduce({}) |$memo, $worker| { $memo + { $worker[0] => { parent => $zone } + $worker[1] } }
 
   class { 'icinga':
     ca            => $_ca,
diff --git a/manifests/worker.pp b/manifests/worker.pp
index f54e845..94d5d6c 100644
--- a/manifests/worker.pp
+++ b/manifests/worker.pp
@@ -46,7 +46,7 @@
   Boolean                      $run_web              = false,
 ) {
   # inject parent zone if no parent exists
-  $_workers = $workers.reduce( {} ) |$memo, $worker| { $memo + { $worker[0] => { parent => $zone } + $worker[1] } }
+  $_workers = $workers.reduce({}) |$memo, $worker| { $memo + { $worker[0] => { parent => $zone } + $worker[1] } }
 
   class { 'icinga':
     ca              => false,