diff --git a/maintenance.py b/maintenance.py
index 2e9e4c1..86cf54e 100644
--- a/maintenance.py
+++ b/maintenance.py
@@ -688,9 +688,10 @@ class CalibrationSample(sequence_ordered(), ModelView, ModelSQL):
                                   ondelete='CASCADE')
     product = fields.Function(fields.Integer("Product ID"), 'get_product_id')
     number_sample = fields.Float("Sample #",  _digits)
-    value_patterns = fields.Many2One('optical_equipment.product_pattern', "Value Pattern", required=True,
+    value_patterns = fields.Many2One('optical_equipment.product_pattern', "Value Pattern", ondelete='RESTRICT', required=True,
                                      domain=[('product', '=', Eval('product'))],
-                                     ondelete='RESTRICT')
+                                     depends=['product']
+                                     )
     value_equipment = fields.Float("Value in Equipment",  _digits, required=True,
                                    states={'readonly': Eval('value_patterns') == None})
     mistake = fields.Float("Mistake",  _digits)