diff --git a/addons/purchase/purchase.py b/addons/purchase/purchase.py
index f52bdeea89c..90f5992b584 100644
--- a/addons/purchase/purchase.py
+++ b/addons/purchase/purchase.py
@@ -401,6 +401,7 @@ class purchase_order(osv.osv):
         return False
 
     def action_cancel(self, cr, uid, ids, context=None):
+        wf_service = netsvc.LocalService("workflow")
         for purchase in self.browse(cr, uid, ids, context=context):
             for pick in purchase.picking_ids:
                 if pick.state not in ('draft','cancel'):
@@ -408,7 +409,6 @@ class purchase_order(osv.osv):
                         _('Unable to cancel this purchase order!'),
                         _('You must first cancel all receptions related to this purchase order.'))
             for pick in purchase.picking_ids:
-                wf_service = netsvc.LocalService("workflow")
                 wf_service.trg_validate(uid, 'stock.picking', pick.id, 'button_cancel', cr)
             for inv in purchase.invoice_ids:
                 if inv and inv.state not in ('cancel','draft'):
@@ -416,10 +416,11 @@ class purchase_order(osv.osv):
                         _('Unable to cancel this purchase order!'),
                         _('You must first cancel all invoices related to this purchase order.'))
                 if inv:
-                    wf_service = netsvc.LocalService("workflow")
                     wf_service.trg_validate(uid, 'account.invoice', inv.id, 'invoice_cancel', cr)
         self.write(cr,uid,ids,{'state':'cancel'})
-        for (id,name) in self.name_get(cr, uid, ids):
+        
+        for (id, name) in self.name_get(cr, uid, ids):
+            wf_service.trg_validate(uid, 'purchase.order', id, 'purchase_cancel', cr)
             message = _("Purchase order '%s' is cancelled.") % name
             self.log(cr, uid, id, message)
         return True
diff --git a/addons/purchase/purchase_workflow.xml b/addons/purchase/purchase_workflow.xml
index aea6fa2b2ac..c978712c0a1 100644
--- a/addons/purchase/purchase_workflow.xml
+++ b/addons/purchase/purchase_workflow.xml
@@ -138,12 +138,12 @@
         <record id="trans_except_picking" model="workflow.transition">
             <field name="act_from" ref="act_except_picking"/>
             <field name="act_to" ref="act_cancel"/>
-            <field name="signal">cancel</field>
+            <field name="signal">purchase_cancel</field>
         </record>
         <record id="trans_except_invoice" model="workflow.transition">
             <field name="act_from" ref="act_except_invoice"/>
             <field name="act_to" ref="act_cancel"/>
-            <field name="signal">cancel</field>
+            <field name="signal">purchase_cancel</field>
         </record>
         <record id="trans_picking_except_picking" model="workflow.transition">
             <field name="act_from" ref="act_picking"/>