--- a/server/src/assets/js/mtdc-tracking-worker.js	Mon Jul 25 18:13:35 2016 +0200
+++ b/server/src/assets/js/mtdc-tracking-worker.js	Mon Jul 25 18:24:03 2016 +0200
@@ -194,8 +194,7 @@
                     data: {
                         'renkan_guid': this.renkan.project.get('id'),
                         'registration': this.registration
-                    },
-                    contentType: 'application/json'
+                    }
                 }).fail(function(){
                     console.log('send tracking data failed');
                 }); // this is fire and forget. Nothong tpo do on failed