diff --git a/example/doc_clone_ptr.cpp b/example/doc_clone_ptr.cpp
index 280c94c..56c0816 100644
--- a/example/doc_clone_ptr.cpp
+++ b/example/doc_clone_ptr.cpp
@@ -30,6 +30,8 @@ class Base
    
    virtual Base *clone() const
    {  return new Base(*this);  }
+
+   virtual ~Base(){}
 };
 
 class Member