Index: branches/features/purchaseOrders/grails-app/domain/PurchaseOrderNumber.groovy
===================================================================
--- branches/features/purchaseOrders/grails-app/domain/PurchaseOrderNumber.groovy	(revision 892)
+++ branches/features/purchaseOrders/grails-app/domain/PurchaseOrderNumber.groovy	(revision 895)
@@ -8,4 +8,5 @@
 
     static constraints = {
+        value(unique:true, blank:false, maxSize:25)
         purchaseOrder(nullable:true)
     }