diff --git a/src/calibre/startup.py b/src/calibre/startup.py
index 96db4d5ae4..ad899d0ca1 100644
--- a/src/calibre/startup.py
+++ b/src/calibre/startup.py
@@ -105,7 +105,7 @@ if not _run_once:
         dl = locale.getdefaultlocale()
         try:
             if dl:
-                locale.setlocale(dl[0])
+                locale.setlocale(locale.LC_ALL, dl[0])
         except:
             pass