diff --git a/company.py b/company.py
index 8a80468359..4d1e3fd02f 100644
--- a/company.py
+++ b/company.py
@@ -6,6 +6,7 @@ from trytond.pyson import Eval
 from trytond.cache import Cache
 from trytond.transaction import Transaction
 from trytond.pool import Pool, PoolMeta
+from trytond import backend
 
 __all__ = ['Employee', 'EmployeeCostPrice']
 __metaclass__ = PoolMeta
@@ -88,11 +89,22 @@ class EmployeeCostPrice(ModelSQL, ModelView):
     currency_digits = fields.Function(fields.Integer('Currency Digits',
             on_change_with=['employee']), 'on_change_with_currency_digits')
 
+    @classmethod
+    def __register__(cls, module_name):
+        TableHandler = backend.get('TableHandler')
+        cursor = Transaction().cursor
+        super(EmployeeCostPrice, cls).__register__(module_name)
+        table = TableHandler(cursor, cls, module_name)
+
+        # Migration from 2.8 drop date_cost_price_uniq
+        table.drop_constraint('date_cost_price_uniq')
+
     @classmethod
     def __setup__(cls):
         super(EmployeeCostPrice, cls).__setup__()
         cls._sql_constraints = [
-            ('date_cost_price_uniq', 'UNIQUE(date, cost_price)',
+            ('employee_date_cost_price_uniq',
+                'UNIQUE(employee, date, cost_price)',
                 'A employee can only have one cost price by date.'),
             ]
         cls._order.insert(0, ('date', 'DESC'))