diff --git a/examples/animals.classes b/examples/animals.classes
index f82b758..a1b686d 100644
--- a/examples/animals.classes
+++ b/examples/animals.classes
@@ -1,11 +1,11 @@
 class Animal
-  public virtual void scream()=0;
+  public pure virtual void scream();
   public std::string getName(); 
   protected std::string name;
 
 class Cat(Animal)
   public virtual void scream();
 
 class Dog(Animal)
   public virtual void scream();