diff --git a/CHANGELOG b/CHANGELOG
index 31e9817077..c2924c4b06 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,4 @@
+* Make language code unique
 * Support base64 encoded data in ModelStorage.import_data
 * Add BOOL_AND and BOOL_OR to SQLite backend
 
diff --git a/trytond/ir/lang.py b/trytond/ir/lang.py
index eaeb6c5094..bbfc38cf8e 100644
--- a/trytond/ir/lang.py
+++ b/trytond/ir/lang.py
@@ -10,7 +10,8 @@ from sql import Table
 from trytond.cache import Cache
 from trytond.exceptions import UserError
 from trytond.i18n import gettext
-from trytond.model import ModelView, ModelSQL, DeactivableMixin, fields, Check
+from trytond.model import (
+    ModelView, ModelSQL, DeactivableMixin, fields, Check, Unique)
 from trytond.modules import create_graph, load_translations
 from trytond.pool import Pool
 from trytond.pyson import Eval
@@ -85,6 +86,8 @@ class Lang(DeactivableMixin, ModelSQL, ModelView):
 
         table = cls.__table__()
         cls._sql_constraints += [
+            ('code_unique', Unique(table, table.code),
+                'ir.msg_language_code_unique'),
             ('check_decimal_point_thousands_sep',
                 Check(table, table.decimal_point != table.thousands_sep),
                 'decimal_point and thousands_sep must be different!'),
diff --git a/trytond/ir/message.xml b/trytond/ir/message.xml
index c02359acac..e24bf735b2 100644
--- a/trytond/ir/message.xml
+++ b/trytond/ir/message.xml
@@ -369,5 +369,8 @@ this repository contains the full copyright notices and license terms. -->
         <record model="ir.message" id="msg_avatar_url">
             <field name="text">Avatar URL</field>
         </record>
+        <record model="ir.message" id="msg_language_code_unique">
+            <field name="text">The code on language must be unique.</field>
+        </record>
     </data>
 </tryton>