diff --git a/src/security/public-key.hpp b/src/security/public-key.hpp
index e939978..b8222c2 100644
--- a/src/security/public-key.hpp
+++ b/src/security/public-key.hpp
@@ -18,10 +18,14 @@
 #define NDN_SECURITY_PUBLIC_KEY_HPP
 
 #include "../common.hpp"
-#include "../encoding/oid.hpp"
+
 #include "../encoding/buffer.hpp"
 #include "security-common.hpp"
 
+namespace CryptoPP {
+class BufferedTransformation;
+}
+
 namespace ndn {
 
 class PublicKey