diff --git a/src/security/signature-sha256-with-ecdsa.hpp b/src/security/signature-sha256-with-ecdsa.hpp
index a20e6b0..4b0eb7f 100644
--- a/src/security/signature-sha256-with-ecdsa.hpp
+++ b/src/security/signature-sha256-with-ecdsa.hpp
@@ -48,6 +48,9 @@
   explicit
   SignatureSha256WithEcdsa(const Signature& signature);
 
+private:
+  void
+  unsetKeyLocator();
 };
 
 } // namespace ndn