--- a/modules/libpref/Preferences.h
+++ b/modules/libpref/Preferences.h
@@ -318,17 +318,17 @@ public:
 
   // Explicitly choosing synchronous or asynchronous (if allowed) preferences
   // file write. Only for the default file.  The guarantee for the "blocking"
   // is that when it returns, the file on disk reflect the current state of
   // preferences.
   nsresult SavePrefFileBlocking();
   nsresult SavePrefFileAsynchronous();
 
-protected:
+private:
   virtual ~Preferences();
 
   nsresult NotifyServiceObservers(const char* aSubject);
 
   // Loads the prefs.js file from the profile, or creates a new one. Returns
   // the prefs file if successful, or nullptr on failure.
   already_AddRefed<nsIFile> ReadSavedPrefs();
 
@@ -356,17 +356,17 @@ protected:
 public:
   // Public so the ValueObserver classes can use it.
   enum MatchKind
   {
     PrefixMatch,
     ExactMatch,
   };
 
-protected:
+private:
   static nsresult RegisterCallback(PrefChangedFunc aCallback,
                                    const char* aPref,
                                    void* aClosure,
                                    MatchKind aMatchKind);
   static nsresult UnregisterCallback(PrefChangedFunc aCallback,
                                      const char* aPref,
                                      void* aClosure,
                                      MatchKind aMatchKind);