diff --git a/modules/purchase_trade/purchase.py b/modules/purchase_trade/purchase.py
index 0ce3a43..5afd049 100755
--- a/modules/purchase_trade/purchase.py
+++ b/modules/purchase_trade/purchase.py
@@ -671,12 +671,14 @@ class Assay(ModelSQL, ModelView):
     date = fields.Date("Analysis Date")
 
     type = fields.Selection([
+        (None, ''),
         ('provisional', 'Provisional'),
         ('final', 'Final'),
         ('umpire', 'Umpire'),
     ], "Type")
 
     status = fields.Selection([
+        (None, ''),
         ('draft', 'Draft'),
         ('validated', 'Validated'),
     ], "Status")