diff --git a/addons/purchase/purchase.py b/addons/purchase/purchase.py
index 5d453686f97..253e8e52fc1 100644
--- a/addons/purchase/purchase.py
+++ b/addons/purchase/purchase.py
@@ -316,7 +316,7 @@ class purchase_order(osv.osv):
         'picking_type_id': fields.many2one('stock.picking.type', 'Deliver To', help="This will determine picking type of incoming shipment", required=True,
                                            states={'confirmed': [('readonly', True)], 'approved': [('readonly', True)], 'done': [('readonly', True)]}),
         'related_location_id': fields.related('picking_type_id', 'default_location_dest_id', type='many2one', relation='stock.location', string="Related location", store=True),
-        'related_usage': fields.related('location_id', 'usage', type='char'),
+        'related_usage': fields.related('location_id', 'usage', type='char', readonly=True),
         'shipment_count': fields.function(_count_all, type='integer', string='Incoming Shipments', multi=True),
         'invoice_count': fields.function(_count_all, type='integer', string='Invoices', multi=True)
     }
@@ -421,6 +421,13 @@ class purchase_order(osv.osv):
             value.update({'related_location_id': picktype.default_location_dest_id.id})
         return {'value': value}
 
+    def onchange_location_id(self, cr, uid, ids, location_id, context=None):
+        value = {'related_usage': False}
+        if location_id:
+            value['related_usage'] = self.pool['stock.location'].browse(cr, uid, location_id, context=context).usage
+        return {'value': value}
+
+
     def onchange_partner_id(self, cr, uid, ids, partner_id, context=None):
         partner = self.pool.get('res.partner')
         if not partner_id:
diff --git a/addons/purchase/purchase_view.xml b/addons/purchase/purchase_view.xml
index 2b22a23890a..cf55d63ae7c 100644
--- a/addons/purchase/purchase_view.xml
+++ b/addons/purchase/purchase_view.xml
@@ -274,7 +274,7 @@
                             <group>
                                 <group>
                                     <field name="minimum_planned_date"/>
-                                    <field name="location_id" groups="stock.group_locations"/>
+                                    <field name="location_id" groups="stock.group_locations" on_change="onchange_location_id(location_id, context)"/>
                                     <field name="shipped" groups="base.group_no_one"/>
                                 </group>
                                 <group>