--- a/browser/modules/DirectoryLinksProvider.jsm
+++ b/browser/modules/DirectoryLinksProvider.jsm
@@ -190,17 +190,17 @@ var DirectoryLinksProvider = {
   get locale() {
     let matchOS;
     try {
       matchOS = Services.prefs.getBoolPref(PREF_MATCH_OS_LOCALE);
     } catch (e) {}
 
     if (matchOS) {
       return Cc["@mozilla.org/intl/ospreferences;1"].
-             getService(Ci.mozIOSPreferences).getSystemLocale();
+             getService(Ci.mozIOSPreferences).systemLocale;
     }
 
     try {
       let locale = Services.prefs.getComplexValue(PREF_SELECTED_LOCALE,
                                                   Ci.nsIPrefLocalizedString);
       if (locale) {
         return locale.data;
       }

--- a/toolkit/components/telemetry/TelemetryEnvironment.jsm
+++ b/toolkit/components/telemetry/TelemetryEnvironment.jsm
@@ -239,17 +239,17 @@ function getBrowserLocale() {
 /**
  * Get the current OS locale.
  * @return a string with the OS locale or null on failure.
  */
 function getSystemLocale() {
   try {
     return Cc["@mozilla.org/intl/ospreferences;1"].
              getService(Ci.mozIOSPreferences).
-             getSystemLocale();
+             systemLocale;
   } catch (e) {
     return null;
   }
 }
 
 /**
  * Safely get a sysinfo property and return its value. If the property is not
  * available, return aDefault.

--- a/toolkit/modules/Locale.jsm
+++ b/toolkit/modules/Locale.jsm
@@ -16,17 +16,17 @@ this.Locale = {
   /**
    * Gets the currently selected locale for display.
    * @return  the selected locale or "en-US" if none is selected
    */
   getLocale() {
     if (Preferences.get(PREF_MATCH_OS_LOCALE, false)) {
       const osPrefs =
         Cc["@mozilla.org/intl/ospreferences;1"].getService(Ci.mozIOSPreferences);
-      return osPrefs.getSystemLocale();
+      return osPrefs.systemLocale;
     }
     try {
       let locale = Preferences.get(PREF_SELECTED_LOCALE, null, Ci.nsIPrefLocalizedString);
       if (locale)
         return locale;
     } catch (e) {}
     return Preferences.get(PREF_SELECTED_LOCALE, "en-US");
   },

--- a/toolkit/mozapps/extensions/AddonManager.jsm
+++ b/toolkit/mozapps/extensions/AddonManager.jsm
@@ -327,17 +327,17 @@ function promiseCallProvider(aProvider, 
  * Gets the currently selected locale for display.
  * @return  the selected locale or "en-US" if none is selected
  */
 function getLocale() {
   try {
     if (Services.prefs.getBoolPref(PREF_MATCH_OS_LOCALE)) {
       const osPrefs =
         Cc["@mozilla.org/intl/ospreferences;1"].getService(Ci.mozIOSPreferences);
-      return osPrefs.getSystemLocale();
+      return osPrefs.systemLocale;
     }
   } catch (e) { }
 
   try {
     let locale = Services.prefs.getComplexValue(PREF_SELECTED_LOCALE,
                                                 Ci.nsIPrefLocalizedString);
     if (locale)
       return locale;