diff --git a/dunning.py b/dunning.py
index 5c139520a0..c9b0a5408c 100644
--- a/dunning.py
+++ b/dunning.py
@@ -130,7 +130,7 @@ class Dunning(ModelSQL, ModelView):
         table = cls.__table__()
         cls._sql_constraints = [
             ('line_unique', Unique(table, table.line),
-                'Line can be used only once on dunning.'),
+                'account_dunning.msg_dunning_line_unique'),
             ]
         cls._active_field = 'active'
 
diff --git a/message.xml b/message.xml
new file mode 100644
index 0000000000..7f65996c53
--- /dev/null
+++ b/message.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0"?>
+<!-- This file is part of Tryton.  The COPYRIGHT file at the top level of
+this repository contains the full copyright notices and license terms. -->
+<tryton>
+    <data group="1">
+        <record model="ir.message" id="msg_dunning_line_unique">
+            <field name="text">Line can be used only once on dunning.</field>
+        </record>
+    </data>
+</tryton>
diff --git a/tryton.cfg b/tryton.cfg
index 72530ae499..b2282ffa91 100644
--- a/tryton.cfg
+++ b/tryton.cfg
@@ -10,3 +10,4 @@ xml:
     dunning.xml
     party.xml
     account.xml
+    message.xml