diff --git a/addons/project/controllers/portal.py b/addons/project/controllers/portal.py
index 798812cb5c2..97e4793dd80 100644
--- a/addons/project/controllers/portal.py
+++ b/addons/project/controllers/portal.py
@@ -417,7 +417,8 @@ class ProjectCustomerPortal(CustomerPortal):
                     grouped_tasks = [Task_sudo.concat(*g) for k, g in groupbyelem(tasks_project_allow_milestone, itemgetter(group))]
 
                     if not grouped_tasks:
-                        grouped_tasks = [tasks_no_milestone]
+                        if tasks_no_milestone:
+                            grouped_tasks = [tasks_no_milestone]
                     else:
                         if grouped_tasks[len(grouped_tasks) - 1][0].milestone_id and tasks_no_milestone:
                             grouped_tasks.append(tasks_no_milestone)