diff --git a/manifests/compute.pp b/manifests/compute.pp
index 4ed6397bb..bb0f6d868 100644
--- a/manifests/compute.pp
+++ b/manifests/compute.pp
@@ -64,8 +64,8 @@
 #
 # [*instance_usage_audit_period*]
 #   (optional) Time period to generate instance usages for.
-#   Time period must be hour, day, month or year
-#   Defaults to 'month'
+#   Time period must be hour, day, month or year with/without offset.
+#   Defaults to $facts['os_service_default']
 #
 # [*use_cow_images*]
 #   (optional) Enable use of copy-on-write (cow) images.
@@ -266,7 +266,7 @@ class nova::compute (
   $vncproxy_path                               = '/vnc_auto.html',
   $force_config_drive                          = false,
   $instance_usage_audit                        = false,
-  $instance_usage_audit_period                 = 'month',
+  $instance_usage_audit_period                 = $facts['os_service_default'],
   $mkisofs_cmd                                 = $facts['os_service_default'],
   $use_cow_images                              = $facts['os_service_default'],
   $force_raw_images                            = $facts['os_service_default'],
@@ -447,7 +447,7 @@ class nova::compute (
     nova_config { 'DEFAULT/force_config_drive': ensure => absent }
   }
 
-  if $instance_usage_audit and $instance_usage_audit_period in ['hour', 'day', 'month', 'year'] {
+  if $instance_usage_audit {
     nova_config {
       'DEFAULT/instance_usage_audit':        value => $instance_usage_audit;
       'DEFAULT/instance_usage_audit_period': value => $instance_usage_audit_period;
diff --git a/spec/classes/nova_compute_spec.rb b/spec/classes/nova_compute_spec.rb
index 8e08ea269..49e72b3e7 100644
--- a/spec/classes/nova_compute_spec.rb
+++ b/spec/classes/nova_compute_spec.rb
@@ -326,16 +326,6 @@ describe 'nova::compute' do
       it { is_expected.to contain_nova_config('DEFAULT/instance_usage_audit_period').with_ensure('absent') }
     end
 
-    context 'with instance_usage_audit parameter and wrong period' do
-      let :params do
-        { :instance_usage_audit        => true,
-          :instance_usage_audit_period => 'fake', }
-      end
-
-      it { is_expected.to contain_nova_config('DEFAULT/instance_usage_audit').with_ensure('absent') }
-      it { is_expected.to contain_nova_config('DEFAULT/instance_usage_audit_period').with_ensure('absent') }
-    end
-
     context 'with instance_usage_audit parameter and period' do
       let :params do
         { :instance_usage_audit        => true,