diff -r 34a75bd8d0b9 -r d48946d164c6 client/src/api/WebAnnotationSerializer.js
--- a/client/src/api/WebAnnotationSerializer.js	Tue Jul 25 19:11:26 2017 +0200
+++ b/client/src/api/WebAnnotationSerializer.js	Fri Jul 28 19:40:35 2017 +0200
@@ -2,14 +2,14 @@
 
   static serialize = (note) => {
 
-    const categories = note.categories;
+    const categories = note.get('categories');
 
     const baseAnnotation = {
       '@context': "http://www.w3.org/ns/anno.jsonld",
       "type":     "Annotation",
     }
 
-    const source = "/session/" + note.session + "/notes/" + note._id;
+    const source = "/session/" + note.get('session') + "/notes/" + note.get('_id');
 
     return categories.map((category, index) => {