diff --git a/project_task_line/__manifest__.py b/project_task_line/__manifest__.py
index 4be1731a..db352855 100644
--- a/project_task_line/__manifest__.py
+++ b/project_task_line/__manifest__.py
@@ -13,6 +13,7 @@ Adds "todo" lines onto Project Tasks, and improves sub-tasks.
         'project',
     ],
     'data': [
+        'security/ir.model.access.csv',
         'views/project_views.xml',
     ],
     'installable': True,
diff --git a/project_task_line/models/project.py b/project_task_line/models/project.py
index a533fffb..9f980c03 100644
--- a/project_task_line/models/project.py
+++ b/project_task_line/models/project.py
@@ -11,7 +11,11 @@ class ProjectTask(models.Model):
     def _compute_subtask_count(self):
         for task in self:
             task.subtask_count = self.search_count([('id', 'child_of', task.id), ('id', '!=', task.id)])
-            task.subtask_count_done = self.search_count([('id', 'child_of', task.id), ('id', '!=', task.id), ('stage_id.fold', '=', True)])
+            if task.subtask_count:
+                task.subtask_count_done = self.search_count([('id', 'child_of', task.id), ('id', '!=', task.id),
+                                                             ('stage_id.fold', '=', True)])
+            else:
+                task.subtask_count_done = 0
 
 
 class ProjectTaskLine(models.Model):
diff --git a/project_task_line/security/ir.model.access.csv b/project_task_line/security/ir.model.access.csv
new file mode 100644
index 00000000..a4846d4f
--- /dev/null
+++ b/project_task_line/security/ir.model.access.csv
@@ -0,0 +1,3 @@
+"id","name","model_id:id","group_id:id","perm_read","perm_write","perm_create","perm_unlink"
+"access_project_task_line","access_project_task_line","model_project_task_line","base.group_user",1,1,1,1
+"access_project_task_line_public","access_project_task_line public","model_project_task_line","base.group_public",1,0,0,0
\ No newline at end of file