diff --git a/mrp_multi_level/data/mrp_area_data.xml b/mrp_multi_level/data/mrp_area_data.xml
index e0334955c..a7c357e6e 100644
--- a/mrp_multi_level/data/mrp_area_data.xml
+++ b/mrp_multi_level/data/mrp_area_data.xml
@@ -1,9 +1,10 @@
 <?xml version="1.0" encoding="utf-8"?>
 <odoo noupdate="1">
+
     <record id="mrp_area_stock_wh0" model="mrp.area">
         <field name="name">WH/Stock</field>
         <field name="warehouse_id" ref="stock.warehouse0"/>
         <field name="location_id" ref="stock.stock_location_stock"/>
-        <field name="calendar_id" ref="resource.resource_calendar_std"/>
     </record>
+
 </odoo>
diff --git a/mrp_multi_level/models/mrp_area.py b/mrp_multi_level/models/mrp_area.py
index 630081a5e..0e400db6e 100644
--- a/mrp_multi_level/models/mrp_area.py
+++ b/mrp_multi_level/models/mrp_area.py
@@ -19,5 +19,8 @@ class MrpArea(models.Model):
         required=True,
     )
     active = fields.Boolean(default=True)
-    calendar_id = fields.Many2one('resource.calendar',
-                                  'Working Hours')
+    calendar_id = fields.Many2one(
+        comodel_name='resource.calendar',
+        string='Working Hours',
+        related='warehouse_id.calendar_id',
+    )
diff --git a/mrp_multi_level/readme/HISTORY.rst b/mrp_multi_level/readme/HISTORY.rst
index 743376125..9ad7e0f12 100644
--- a/mrp_multi_level/readme/HISTORY.rst
+++ b/mrp_multi_level/readme/HISTORY.rst
@@ -3,6 +3,9 @@
 
 * [FIX] User and system locales doesn't break MRP calculation.
   (`#290 <https://github.com/OCA/manufacture/pull/290>`_)
+* [FIX] Working Hours are now defined only at Warehouse level and displayed
+  as a related on MRP Areas.
+  (`#290 <https://github.com/OCA/manufacture/pull/290>`__)
 
 11.0.1.0.0 (2018-07-09)
 ~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/mrp_multi_level/tests/test_mrp_multi_level.py b/mrp_multi_level/tests/test_mrp_multi_level.py
index 979893078..af5fd2268 100644
--- a/mrp_multi_level/tests/test_mrp_multi_level.py
+++ b/mrp_multi_level/tests/test_mrp_multi_level.py
@@ -38,6 +38,8 @@ class TestMrpMultiLevel(SavepointCase):
         cls.customer_location = cls.env.ref(
             'stock.stock_location_customers')
         cls.calendar = cls.env.ref('resource.resource_calendar_std')
+        # Add calendar to WH:
+        cls.wh.calendar_id = cls.calendar
 
         # Partner:
         vendor1 = cls.partner_obj.create({'name': 'Vendor 1'})
@@ -367,9 +369,8 @@ class TestMrpMultiLevel(SavepointCase):
             ('product_id', '=', self.fp_1.id)])
         self.assertTrue(mos)
         self.assertEqual(mos.product_qty, 100.0)
-        datetime_5 = fields.Datetime.to_string(
-            self.calendar.plan_days(5 + 1, datetime.today()).date())
-        self.assertEqual(mos.date_planned_start, datetime_5)
+        mo_date_start = mos.date_planned_start.split(' ')[0]
+        self.assertEqual(mo_date_start, self.date_5)
 
     # TODO: test procure wizard: pos, multiple...
     # TODO: test multiple destination IDS:...
diff --git a/mrp_multi_level/wizards/mrp_multi_level.py b/mrp_multi_level/wizards/mrp_multi_level.py
index 0d1f35e3d..fbe837af6 100644
--- a/mrp_multi_level/wizards/mrp_multi_level.py
+++ b/mrp_multi_level/wizards/mrp_multi_level.py
@@ -274,11 +274,7 @@ class MultiLevelMrp(models.TransientModel):
                                 mrp_date_demand_2,
                                 bom, name)
                         mrpmove_id2 = self.env['mrp.move'].create(move_data)
-                        sql_stat = "INSERT INTO mrp_move_rel (" \
-                                   "move_up_id, " \
-                                   "move_down_id) values (%d, %d)" % \
-                                   (mrpmove_id, mrpmove_id2, )
-                        self.env.cr.execute(sql_stat)
+                        mrpmove_id.mrp_move_down_ids = [(4, mrpmove_id2.id)]
         values['qty_ordered'] = qty_ordered
         log_msg = '%s' % qty_ordered
         logger.info(log_msg)