diff --git a/src/fleetcommanderclient/configadapters/firefoxbookmarks.py b/src/fleetcommanderclient/configadapters/firefoxbookmarks.py
index 79990d4..ce2256e 100644
--- a/src/fleetcommanderclient/configadapters/firefoxbookmarks.py
+++ b/src/fleetcommanderclient/configadapters/firefoxbookmarks.py
@@ -63,6 +63,9 @@ def update(self, uid, data):
         bookmarks = []
         for item in data:
             if 'key' in item and 'value' in item:
+                for fld, val in item['value'].items():
+                    if val is None:
+                        item['value'][fld] = ''
                 bookmarks.append(item['value'])
         policies_data = {"policies": {'Bookmarks': bookmarks}}
         # Write preferences data