diff --git a/addons/project_retro_planning/project_retro_planning.py b/addons/project_retro_planning/project_retro_planning.py
index 6360b3cae13..fd50fe64e50 100644
--- a/addons/project_retro_planning/project_retro_planning.py
+++ b/addons/project_retro_planning/project_retro_planning.py
@@ -27,8 +27,10 @@ from osv import fields, osv
 class project_project(osv.osv):
     _inherit = 'project.project'
 
-    def write(self, cr, uid, ids,vals, *args, **kwargs):
-        if 'date' in vals and vals['date']:
+    def write(self, cr, uid, ids, vals, *args, **kwargs):
+        if isinstance(ids, (int, long)):
+            ids = [ids]
+        if vals.get('date', False):
             data_project = self.browse(cr, uid, ids)
             for prj in data_project:
                 new_end_date = date(*time.strptime(vals['date'],'%Y-%m-%d')[:3])
@@ -39,9 +41,9 @@ class project_project(osv.osv):
                             start_dt = (date(*time.strptime(str(task.date_start),'%Y-%m-%d  %H:%M:%S')[:3])+(new_end_date-old_end_date)).strftime('%Y-%m-%d %H:%M:%S')
                             if task.date_deadline:
                                 deadline_dt = (datetime(*time.strptime(str(task.date_deadline),'%Y-%m-%d')[:3])+(new_end_date-old_end_date)).strftime('%Y-%m-%d')
-                                self.pool.get('project.task').write(cr, uid, task.id, {'date_start':start_dt, 'date_deadline':deadline_dt})
+                                self.pool.get('project.task').write(cr, uid, [task.id], {'date_start':start_dt, 'date_deadline':deadline_dt})
                             else:
-                                self.pool.get('project.task').write(cr, uid, task.id, {'date_start':start_dt})
+                                self.pool.get('project.task').write(cr, uid, [task.id], {'date_start':start_dt})
         return super(project_project,self).write(cr, uid, ids, vals, *args, **kwargs)
 
 project_project()