diff --git a/src/class_extension/relation_to_encapsulation.md b/src/class_extension/relation_to_encapsulation.md
index 6faa05a..36f2786 100644
--- a/src/class_extension/relation_to_encapsulation.md
+++ b/src/class_extension/relation_to_encapsulation.md
@@ -72,7 +72,8 @@ class Airplane {
 
     void bookMany(List<String> passengers) {
         for (var passenger : passengers) {
-            bookOne(passenger);
+            // Only change
+            this.passengers.add(passenger);
         }
     }
 }