diff --git a/src/security/transform/private-key.hpp b/src/security/transform/private-key.hpp
index 98f5bd6..17d582b 100644
--- a/src/security/transform/private-key.hpp
+++ b/src/security/transform/private-key.hpp
@@ -22,6 +22,7 @@
 #ifndef NDN_CXX_SECURITY_TRANSFORM_PRIVATE_KEY_HPP
 #define NDN_CXX_SECURITY_TRANSFORM_PRIVATE_KEY_HPP
 
+#include "../security-common.hpp"
 #include "../../encoding/buffer.hpp"
 
 namespace ndn {
@@ -68,6 +69,12 @@
   ~PrivateKey();
 
   /**
+   * @brief Get the type of the private key
+   */
+  KeyType
+  getKeyType() const;
+
+  /**
    * @brief Load the private key in PKCS#1 format from a buffer @p buf
    */
   void