diff --git a/src/security/validator-null.hpp b/src/security/validator-null.hpp
index 90b5293..27dc63d 100644
--- a/src/security/validator-null.hpp
+++ b/src/security/validator-null.hpp
@@ -14,22 +14,22 @@
 namespace ndn {
 
 class ValidatorNull : public Validator {
-protected:
-
+public:
   virtual
   ~ValidatorNull()
   {}
-
+  
+protected:
   virtual void
-  checkPolicy (shared_ptr<const Data> data, 
+  checkPolicy (const shared_ptr<const Data>& data, 
                int stepCount, 
                const OnDataValidated &onValidated, 
                const OnDataValidationFailed &onValidationFailed,
                std::vector<shared_ptr<ValidationRequest> > &nextSteps)
   { onValidated(data); }
-
+  
   virtual void
-  checkPolicy (shared_ptr<const Interest> interest, 
+  checkPolicy (const shared_ptr<const Interest>& interest, 
                int stepCount, 
                const OnInterestValidated &onValidated, 
                const OnInterestValidationFailed &onValidationFailed,
diff --git a/src/security/validator-regex.hpp b/src/security/validator-regex.hpp
index e080ddf..a06964c 100644
--- a/src/security/validator-regex.hpp
+++ b/src/security/validator-regex.hpp
@@ -51,12 +51,20 @@
 
 protected:
   virtual void
-  checkPolicy (const shared_ptr<const Data> &data, 
+  checkPolicy (const shared_ptr<const Data>& data, 
                int stepCount, 
                const OnDataValidated &onValidated, 
                const OnDataValidationFailed &onValidationFailed,
                std::vector<shared_ptr<ValidationRequest> > &nextSteps);
 
+  virtual void
+  checkPolicy (const shared_ptr<const Interest>& interest, 
+               int stepCount, 
+               const OnInterestValidated &onValidated, 
+               const OnInterestValidationFailed &onValidationFailed,
+               std::vector<shared_ptr<ValidationRequest> > &nextSteps)
+  { onValidationFailed(interest); }
+
   void
   onCertificateValidated(const shared_ptr<const Data> &signCertificate, 
                          const shared_ptr<const Data> &data, 
diff --git a/src/security/validator.hpp b/src/security/validator.hpp
index 82f8e98..4ba4c43 100644
--- a/src/security/validator.hpp
+++ b/src/security/validator.hpp
@@ -97,8 +97,7 @@
                int stepCount, 
                const OnDataValidated &onValidated, 
                const OnDataValidationFailed &onValidationFailed,
-               std::vector<shared_ptr<ValidationRequest> > &nextSteps)
-  { onValidationFailed(data); }
+               std::vector<shared_ptr<ValidationRequest> > &nextSteps) = 0;
 
   /**
    * @brief Check the Interest against validation policy and return the next validation step if necessary.
@@ -117,8 +116,7 @@
                int stepCount, 
                const OnInterestValidated &onValidated, 
                const OnInterestValidationFailed &onValidationFailed,
-               std::vector<shared_ptr<ValidationRequest> > &nextSteps)
-  { onValidationFailed(interest); }
+               std::vector<shared_ptr<ValidationRequest> > &nextSteps) = 0;
 
 private:
   typedef function< void () > OnFailure;