diff --git a/index.js b/index.js
index 85d0430..b2acc98 100644
--- a/index.js
+++ b/index.js
@@ -58,7 +58,7 @@ var xml = function(options) {
             icon.element(r.type, r.uri, (r.creativeType) ? { creativeType : r.creativeType } : {});
           });
         });
-        creativeType.element('Duration', c.Duration);
+        if (c.Duration) creativeType.element('Duration', c.Duration);
         var trackingEvents = creativeType.element('TrackingEvents');
         c.trackingEvents.forEach(function(trackingEvent){
           if (track) {
@@ -72,10 +72,12 @@ var xml = function(options) {
         c.videoClicks.forEach(function(videoClick){
           videoClicks.element(videoClick.type, videoClick.url, { id : videoClick.id });
         });
-        var mediaFiles = creativeType.element('MediaFiles');
-        c.mediaFiles.forEach(function(mediaFile) {
-          mediaFiles.element('MediaFile', mediaFile.attributes).cdata(mediaFile.url);
-        });
+        if (c.mediaFiles && c.mediaFiles.length > 0) {
+          var mediaFiles = creativeType.element('MediaFiles');
+          c.mediaFiles.forEach(function(mediaFile) {
+            mediaFiles.element('MediaFile', mediaFile.attributes).cdata(mediaFile.url);
+          });
+        }
       });
 
       nonLinearCreatives.forEach(function(c){
diff --git a/lib/creative.js b/lib/creative.js
index 1d963eb..b757c60 100644
--- a/lib/creative.js
+++ b/lib/creative.js
@@ -9,7 +9,7 @@ function Creative(type, settings) {
 
   if (settings.Duration) {
     this.Duration = settings.Duration;    
-  } else if (type === 'Linear') {
+  } else if (type === 'Linear' && !settings.Wrapper) {
     throw new Error('A Duration is required for all creatives. Consider defaulting to "00:00:00"');
   }
   this.attributes = {};
diff --git a/test/wrapper.test.js b/test/wrapper.test.js
index ae10dce..794275c 100644
--- a/test/wrapper.test.js
+++ b/test/wrapper.test.js
@@ -1,6 +1,8 @@
 var test = require('tap').test
   , VAST = require('../index.js')
-  , vast = new VAST();
+  , vast = new VAST()
+  , ad
+  , creative;
 
 test('Validate ad settings', function(t){
   t.throws(function(){
@@ -21,7 +23,7 @@ test('Validate ad settings', function(t){
   t.end();
 });
 
-vast.attachAd({ 
+ad = vast.attachAd({
     structure : 'wrapper'
   , AdSystem : 'Common name of the ad'
   , sequence : 23
@@ -29,4 +31,6 @@ vast.attachAd({
   , VASTAdTagURI : 'http://example.com'
 }).attachImpression({ id: Date.now(), url : 'http://impression.com' });
 
+creative = ad.attachCreative('Linear', { Wrapper : true } )
+
 module.exports = vast;