diff --git a/manifests/plugins/ml2/type_driver.pp b/manifests/plugins/ml2/type_driver.pp
index 78c085da7..b15869590 100644
--- a/manifests/plugins/ml2/type_driver.pp
+++ b/manifests/plugins/ml2/type_driver.pp
@@ -130,6 +130,6 @@ define neutron::plugins::ml2::type_driver (
   }
   else {
     # detect an invalid type_drivers value
-    fail('type_driver unknown.')
+    warning('type_driver unknown.')
   }
 }
diff --git a/spec/classes/neutron_plugins_ml2_spec.rb b/spec/classes/neutron_plugins_ml2_spec.rb
index 4c0fbce22..c4278d565 100644
--- a/spec/classes/neutron_plugins_ml2_spec.rb
+++ b/spec/classes/neutron_plugins_ml2_spec.rb
@@ -154,10 +154,9 @@ describe 'neutron::plugins::ml2' do
 
     context 'configure ml2 with bad driver value' do
       before :each do
+       scope.expects(:warning).with('type_driver unknown.')
        params.merge!(:type_drivers => ['foobar'])
       end
-
-      it_raises 'a Puppet::Error', /type_driver unknown./
     end
 
     context 'when using flat driver' do