diff --git a/odoo/models.py b/odoo/models.py
index 97787970d51..eca249f6200 100644
--- a/odoo/models.py
+++ b/odoo/models.py
@@ -519,7 +519,7 @@ class BaseModel(MetaModel('DummyModel', (object,), {'_register': False})):
         cls._inherits = {}
         cls._depends = {}
         cls._constraints = {}
-        cls._sql_constraints = []
+        cls._sql_constraints = {}
 
         for base in reversed(cls.__bases__):
             if not getattr(base, 'pool', None):
@@ -540,10 +540,12 @@ class BaseModel(MetaModel('DummyModel', (object,), {'_register': False})):
                 # cons may override a constraint with the same function name
                 cls._constraints[getattr(cons[0], '__name__', id(cons[0]))] = cons
 
-            cls._sql_constraints += base._sql_constraints
+            for cons in base._sql_constraints:
+                cls._sql_constraints[cons[0]] = cons
 
         cls._sequence = cls._sequence or (cls._table + '_id_seq')
         cls._constraints = list(cls._constraints.values())
+        cls._sql_constraints = list(cls._sql_constraints.values())
 
         # update _inherits_children of parent models
         for parent_name in cls._inherits: