diff --git a/carrier.py b/carrier.py
index 445fff6428..b2192ce817 100644
--- a/carrier.py
+++ b/carrier.py
@@ -1,5 +1,7 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
+import locale
+
 from zeep.exceptions import Fault
 
 from trytond.model import ModelSQL, ModelView, MatchMixin, fields
@@ -40,6 +42,7 @@ class CredentialDPD(ModelSQL, ModelView, MatchMixin):
         auth_client = get_client(self.server, LOGIN_SERVICE)
         lang = (self.company.party.lang.code
             if self.company.party.lang else 'en')
+        lang = locale.normalize(lang)[:5]
         try:
             result = auth_client.service.getAuth(
                 delisId=self.user_id, password=self.password,
diff --git a/stock.py b/stock.py
index b7ded5ced4..0913795f18 100644
--- a/stock.py
+++ b/stock.py
@@ -1,6 +1,7 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
 
+import locale
 from io import BytesIO
 from lxml import etree
 from zeep.exceptions import Fault
@@ -102,6 +103,7 @@ class CreateDPDShipping(Wizard):
         while count < 2:
             lang = (credential.company.party.lang.code
                 if credential.company.party.lang else 'en')
+            lang = locale.normalize(lang)[:5]
             authentication = {
                 'delisId': credential.user_id,
                 'authToken': credential.token,