diff --git a/modules/libpref/src/init/all.js b/modules/libpref/src/init/all.js
index 4e40cfa..b44ec96 100644
--- a/modules/libpref/src/init/all.js
+++ b/modules/libpref/src/init/all.js
@@ -1024,7 +1024,7 @@ pref("intl.charsetmenu.browser.cache.size", 5);
 pref("intl.charset.detector",               "chrome://global/locale/intl.properties");
 pref("intl.charset.default",                "chrome://global-platform/locale/intl.properties");
 pref("intl.ellipsis",                       "chrome://global-platform/locale/intl.properties");
-pref("intl.locale.matchOS",                 false);
+pref("intl.locale.matchOS",                 true);
 // fallback charset list for Unicode conversion (converting from Unicode)
 // currently used for mail send only to handle symbol characters (e.g Euro, trademark, smartquotes)
 // for ISO-8859-1