diff --git a/ndn-cpp/security/certificate/certificate-extension.cpp b/ndn-cpp/security/certificate/certificate-extension.cpp
index aba88dd..d3719a7 100644
--- a/ndn-cpp/security/certificate/certificate-extension.cpp
+++ b/ndn-cpp/security/certificate/certificate-extension.cpp
@@ -20,6 +20,7 @@
 shared_ptr<der::DerNode> 
 CertificateExtension::toDer()
 {
+#if 0 // Include again when der is defined.
   shared_ptr<der::DerSequence> root(new der::DerSequence);
     
   shared_ptr<der::DerOid> extensionId(new der::DerOid(extensionId_));
@@ -33,6 +34,9 @@
   root->getSize();
 
   return root;
+#else
+  throw std::runtime_error("not implemented");
+#endif
 }
 
 Blob
diff --git a/ndn-cpp/security/certificate/certificate-subject-description.cpp b/ndn-cpp/security/certificate/certificate-subject-description.cpp
index ee2310c..e66b672 100644
--- a/ndn-cpp/security/certificate/certificate-subject-description.cpp
+++ b/ndn-cpp/security/certificate/certificate-subject-description.cpp
@@ -6,6 +6,9 @@
  * See COPYING for copyright and distribution information.
  */
 
+#if 1 // TODO: Remove this when we don't throw "not implemented".
+#include <stdexcept>
+#endif
 #include "../../encoding/der/der.hpp"
 #include <ndn-cpp/security/certificate/certificate-subject-description.hpp>
 
@@ -17,6 +20,7 @@
 shared_ptr<der::DerNode> 
 CertificateSubjectDescription::toDer()
 {
+#if 0 // Include again when der is defined.
   shared_ptr<der::DerSequence> root(new der::DerSequence());
 
   shared_ptr<der::DerOid> oid(new der::DerOid(oid_));
@@ -26,6 +30,9 @@
   root->addChild(value);
 
   return root;
+#else
+  throw std::runtime_error("not implemented");
+#endif
 }
 
 }