diff --git a/manifests/plugins/ml2/ovs_driver.pp b/manifests/plugins/ml2/ovs_driver.pp
index fa27fafb2..774b8c521 100644
--- a/manifests/plugins/ml2/ovs_driver.pp
+++ b/manifests/plugins/ml2/ovs_driver.pp
@@ -23,9 +23,14 @@ class neutron::plugins::ml2::ovs_driver (
   $vnic_type_blacklist = [],
 ){
 
+  validate_legacy(Array, 'validate_array', $vnic_type_blacklist)
   if !empty($vnic_type_blacklist) {
     neutron_plugin_ml2 {
       'ovs_driver/vnic_type_blacklist': value => join(any2array($vnic_type_blacklist), ',');
     }
+  } else {
+    neutron_plugin_ml2 {
+      'ovs_driver/vnic_type_blacklist': value => $::os_service_default;
+    }
   }
 }
diff --git a/manifests/plugins/ml2/sriov_driver.pp b/manifests/plugins/ml2/sriov_driver.pp
index 513f8a0e5..c14df7006 100644
--- a/manifests/plugins/ml2/sriov_driver.pp
+++ b/manifests/plugins/ml2/sriov_driver.pp
@@ -23,9 +23,14 @@ class neutron::plugins::ml2::sriov_driver (
   $vnic_type_blacklist= [],
 ){
 
+  validate_legacy(Array, 'validate_array', $vnic_type_blacklist)
   if !empty($vnic_type_blacklist) {
     neutron_plugin_ml2 {
       'sriov_driver/vnic_type_blacklist': value => join(any2array($vnic_type_blacklist), ',');
     }
+  } else {
+    neutron_plugin_ml2 {
+      'sriov_driver/vnic_type_blacklist': value => $::os_service_default;
+    }
   }
 }
diff --git a/spec/classes/neutron_plugins_ml2_ovs_driver_spec.rb b/spec/classes/neutron_plugins_ml2_ovs_driver_spec.rb
index 893cf631d..96f429ea6 100644
--- a/spec/classes/neutron_plugins_ml2_ovs_driver_spec.rb
+++ b/spec/classes/neutron_plugins_ml2_ovs_driver_spec.rb
@@ -17,6 +17,16 @@ require 'spec_helper'
 describe 'neutron::plugins::ml2::ovs_driver' do
 
   shared_examples 'neutron::plugins::ml2::ovs_driver' do
+    context 'with defaults' do
+      let :params do
+        {}
+      end
+
+      it 'should set the default values' do
+        should contain_neutron_plugin_ml2('ovs_driver/vnic_type_blacklist').with_value("<SERVICE DEFAULT>")
+      end
+    end
+
     context 'when vnic_type_blacklist is not empty list' do
       let :params do
         { :vnic_type_blacklist => ['direct'] }
diff --git a/spec/classes/neutron_plugins_ml2_sriov_driver_spec.rb b/spec/classes/neutron_plugins_ml2_sriov_driver_spec.rb
index c0cae55ba..fd83f6e84 100644
--- a/spec/classes/neutron_plugins_ml2_sriov_driver_spec.rb
+++ b/spec/classes/neutron_plugins_ml2_sriov_driver_spec.rb
@@ -17,6 +17,16 @@ require 'spec_helper'
 describe 'neutron::plugins::ml2::sriov_driver' do
 
   shared_examples 'neutron::plugins::ml2::sriov_driver' do
+    context 'with defaults' do
+      let :params do
+        {}
+      end
+
+      it 'should set the default values' do
+        should contain_neutron_plugin_ml2('sriov_driver/vnic_type_blacklist').with_value("<SERVICE DEFAULT>")
+      end
+    end
+
     context 'when vnic_type_blacklist is not empty list' do
       let :params do
         { :vnic_type_blacklist => ['direct'] }