diff --git a/modoboa/core/constants.py b/modoboa/core/constants.py
index e87f70b52..271d91015 100644
--- a/modoboa/core/constants.py
+++ b/modoboa/core/constants.py
@@ -26,20 +26,20 @@ LANGUAGES = (
     ("cs", u"čeština"),
     ("de", u"deutsch"),
     ("en", u"english"),
-    ("el_GR", u"ελληνικά"),
+    ("el", u"ελληνικά"),
     ("es", u"español"),
     ("fr", u"français"),
     ("it", u"italiano"),
-    ("ja_JP", u"日本の"),
+    ("ja", u"日本の"),
     ("nl", u"nederlands"),
-    ("pt_PT", u"português"),
-    ("pt_BR", u"português (BR)"),
-    ("pl_PL", u"polski"),
-    ("ro_RO", u"Română"),
+    ("pt", u"português"),
+    ("pt-br", u"português (BR)"),
+    ("pl", u"polski"),
+    ("ro", u"Română"),
     ("ru", u"русский"),
     ("sv", u"svenska"),
-    ("tr_TR", u"türk"),
-    ("zh_TW", u"中文（台灣）"),
+    ("tr", u"türk"),
+    ("zh-hant", u"中文（台灣）"),
 )