diff --git a/attract/task_manager.py b/attract/task_manager.py
index 8e8ada2..16137df 100644
--- a/attract/task_manager.py
+++ b/attract/task_manager.py
@@ -70,7 +70,11 @@ class TaskManager(object):
         task.description = fields.pop('description')
         task.properties.status = fields.pop('status')
         task.properties.task_type = fields.pop('task_type', '').strip() or None
-        task.properties.assigned_to = {'users': fields.pop('users')}
+
+        users = fields.pop('users', None)
+        if users:
+            task.properties.assigned_to = {'users': users}
+
         self._log.info('Saving task %s', task.to_dict())
 
         if fields: