diff --git a/helper/ccnb-parser/visitors/ccnb-parser-no-argu-visitor.h b/helper/ccnb-parser/visitors/ccnb-parser-no-argu-visitor.h
index 6f6bcc2..ce3e712 100644
--- a/helper/ccnb-parser/visitors/ccnb-parser-no-argu-visitor.h
+++ b/helper/ccnb-parser/visitors/ccnb-parser-no-argu-visitor.h
@@ -44,6 +44,8 @@
   virtual boost::any visit (Dtag& )=0; ///< \brief Method accepting DTAG block  
   virtual boost::any visit (Dattr&)=0; ///< \brief Method accepting DATTR block 
   virtual boost::any visit (Ext&  )=0; ///< \brief Method accepting EXT block
+
+  virtual ~NoArguVisitor () { }
 };
   
 }
diff --git a/helper/ccnb-parser/visitors/ccnb-parser-visitor.h b/helper/ccnb-parser/visitors/ccnb-parser-visitor.h
index 24212d4..e0fac3a 100644
--- a/helper/ccnb-parser/visitors/ccnb-parser-visitor.h
+++ b/helper/ccnb-parser/visitors/ccnb-parser-visitor.h
@@ -44,6 +44,8 @@
   virtual boost::any visit (Dtag&,  boost::any)=0; ///< \brief Method accepting DTAG block  
   virtual boost::any visit (Dattr&, boost::any)=0; ///< \brief Method accepting DATTR block 
   virtual boost::any visit (Ext&,   boost::any)=0; ///< \brief Method accepting EXT block
+
+  virtual ~Visitor () { }
 };                                                
                                                   
 }                                                 
diff --git a/helper/ccnb-parser/visitors/ccnb-parser-void-no-argu-visitor.h b/helper/ccnb-parser/visitors/ccnb-parser-void-no-argu-visitor.h
index 975c0c6..ad0ff74 100644
--- a/helper/ccnb-parser/visitors/ccnb-parser-void-no-argu-visitor.h
+++ b/helper/ccnb-parser/visitors/ccnb-parser-void-no-argu-visitor.h
@@ -43,6 +43,8 @@
   virtual void visit (Dtag& )=0; ///< \brief Method accepting DTAG block
   virtual void visit (Dattr&)=0; ///< \brief Method accepting DATTR block
   virtual void visit (Ext&  )=0; ///< \brief Method accepting EXT block
+
+  virtual ~VoidNoArguVisitor () { }
 };
   
 }
diff --git a/helper/ccnb-parser/visitors/ccnb-parser-void-visitor.h b/helper/ccnb-parser/visitors/ccnb-parser-void-visitor.h
index 9b45836..4fd228d 100644
--- a/helper/ccnb-parser/visitors/ccnb-parser-void-visitor.h
+++ b/helper/ccnb-parser/visitors/ccnb-parser-void-visitor.h
@@ -44,6 +44,8 @@
   virtual void visit (Dtag&,  boost::any)=0; ///< \brief Method accepting DTAG block  
   virtual void visit (Dattr&, boost::any)=0; ///< \brief Method accepting DATTR block 
   virtual void visit (Ext&,   boost::any)=0; ///< \brief Method accepting EXT block
+
+  virtual ~VoidVisitor () { }
 };
 
 }