diff --git a/tryton/translate.py b/tryton/translate.py
index ac5bf2ac06..b7f93bbc62 100644
--- a/tryton/translate.py
+++ b/tryton/translate.py
@@ -164,7 +164,7 @@ def setlang(lang=None):
             lang2 = lang
             if os.name == 'nt':
                 lang2 = _LOCALE2WIN32.get(lang, lang)
-            locale.setlocale(locale.LC_ALL, lang2 + '.' + encoding)
+            locale.setlocale(locale.LC_ALL, str(lang2 + '.' + encoding))
         except:
             logging.getLogger('translate').info(
                     _('Unable to set locale %s') % lang2 + '.' + encoding)