diff --git a/src/effectivejava/chapter5/item33/Favorites.java b/src/effectivejava/chapter5/item33/Favorites.java
index 4e3385f7d..da6bdab6a 100644
--- a/src/effectivejava/chapter5/item33/Favorites.java
+++ b/src/effectivejava/chapter5/item33/Favorites.java
@@ -3,7 +3,7 @@
 
 // Typesafe heterogeneous container pattern (Pages 151-4)
 public class Favorites {
-    private Map<Class<?>, Object> favorites = new HashMap<>();
+    private final Map<Class<?>, Object> favorites = new HashMap<>();
 
     public <T> void putFavorite(Class<T> type, T instance) {
         favorites.put(Objects.requireNonNull(type), instance);
@@ -29,4 +29,4 @@ public static void main(String[] args) {
         System.out.printf("%s %x %s%n", favoriteString,
                 favoriteInteger, favoriteClass.getName());
     }
-}
\ No newline at end of file
+}